题目内容
（请给出正确答案）
The usual symptoms of cavitation in a centrifugal pump is _____.
A.noise and vibration
B.an increase in discharge pressure
C.an increase in suction pressure
D.lifting of the relief valve
简答题官方参考答案
（由简答题聘请的专业题库老师提供的解答）
更多“The usual symptoms of cavitation in a centrifugal pump is _____.A.noise and vibrationB.an”相关的问题
usual)
The usual method of effectively applying foam on a fire is by ______.
A.spraying directly on the base of the fire
B.flowing the foam down a vertical surface
C.sweeping the fire before you with the foam
D.spraying directly on the surface of the fire
On which of the following would the author most probably agree？
A．We might as well google our symptoms instead of turning to shrinks.
B．Arnall"s theory has been discounted in that it does not quite fit the fact.
C．There lies a relation between the demographics of visitors and their incomes.
D．Depression during November primarily affects the young and the old.
Now, listen to the conversation.
What is the disadvantage of an excursion fare？
[A] More expensive than the usual price.
[B] Only one stopover allowed.
[C] Having only one Australian stop.
[D] Many restrictions on it.
PARAPAIN(25 TABLETS BP. )
For headache, rheumatic pains, neuralgia and relief of symptoms of colds and influenza.
DOSE UNLESS OTHERWISE DIRECTED BY A DOCTOR
Adult and children over 12 years, swallow one to two tablets with water. Dose should not be repeated more frequently than 4 hours intervals and not more than 4 times in any 24 hour period.
DO NOT EXCEED THE STATED DOSE.
AN OVERDOSE IS DANGEROUS.
MEDICAL ATTENTION SHOULD BE SOUGHT IMMEDIATELY.
Which of the following statements is true according to the medicine label？
A．Parapain can be used to cure the colds and flu.
B．You cannot take the Parapain without the doctor's instructions.
C．He or she must be sent to see a doctor at once when overdosing Parapain.
D．Each bottle of Parapain contains 15 tablets.
Some scientists have concluded that narcolepsy, a disease which disrupts
sleep patterns, arises when unknown agents in the environment spur an
autoimmune reaction winding up damaging neurons in the brain circuits that Line
control arousal and muscle tone. Honda found that all members of a group of
(5) narcoleptics had one aspect of their tissue type in common, one of the human
leukocyte antigens (HLAs). Whereas the HLA type was clearly not sufficient to
induce narcolepsy, Honda's finding indicated that HLA type greatly affected
susceptibility to the disease. HLA molecules are pitchfork-shaped structures that
cells of the body use to show pieces of the proteins they contain to the immune
(10) system, which ordinarily attacks foreign substances and cells infected by
viruses.
Evidence for an autoimmune cause of narcolepsy will most likely come from
studies of the brains of people who had the disorder. Ever since Gineau
correctly named narcolepsy as a distinct syndrome in 1880, researchers have
(15) examined the brains of patients in a futile search for neurological damage that
could explain the symptoms of the disease. Mignot observed that the brains of
narcoleptic dogs had more than the usual number of receptors for the
neurotransmitters acetylcholine, dopamine and norepinephrine and higher levels
of some of the neurotransmitters themselves, changes identical to those Aldrich
(20) later noted human narcoleptic brains.
Given that narcolepsy is not progressive but chronic—i.e. after the
establishment of symptoms, narcoleptics do not deteriorate or improve-
pathologists may have been focusing their efforts on the wrong stage of the
disease's progression. This suggested that the damage might occur during a
(25) short time, roughly during the period in which a patient first develops signs of
the illness. Debris left over from degenerative processes that occurred at the
age of 20 would be removed by the brain's support cells long before most
patients died, and any remaining clues would be obscured by the normal
degeneration of aging. As a loss of neurons would be undetectable unless the
(30) dead cells were concentrated in a particular area, as in Parkinson's disease, or
unless many neurons died, as in Alzheimer's disease, I therefore examined the
brains of narcoleptic dogs shortly after their symptoms had begun, and found
clear evidence that neurons in certain areas of the dogs' brains were
degenerating between one and two months of age, just before and during the
(35) onset of symptoms. Evidence of the degeneration largely disappeared by the
time the dogs were six months old. At this moment, all we can give patients are
drugs to treat narcolepsy's symptoms, even though this research promises the
definite potential of a cure.
In the passage, the author is primarily concerned with
A．presenting a hypothesis and describing compelling evidence in support of it
B．raising a question and describing an important discovery that led to an answer
C．showing that a certain autoimmune disease cannot yet be treated effectively with drugs
D．explaining what evidence exists for an autoimmune cause for narcolepsy
E．discussing the importance of research on animals for the study of human disease
Some scientists have concluded that narcolepsy, a disease which disrupts
sleep patterns, arises when unknown agents in the environment spur an
autoimmune reaction winding up damaging neurons in the brain circuits that
control arousal and muscle tone. Honda found that all members of a group of
(5) narcoleptics had one aspect of their tissue type in common, one of the human
leukocyte antigens (HLAs). Whereas the HLA type was clearly not sufficient to
induce narcolepsy, Honda's finding indicated that HLA type greatly affected
susceptibility to the disease. HLA molecules are pitchfork-shaped structures that
cells of the body use to show pieces of the proteins they contain to the immune
(10) system, which ordinarily attacks foreign substances and cells infected by
viruses.
Evidence for an autoimmune cause of narcolepsy will most likely come from
studies of the brains of people who had the disorder. Ever since Gineau
correctly named narcolepsy as a distinct syndrome in 1880, researchers have
(15) examined the brains of patients in a futile search for neurological damage that
could explain the symptoms of the disease. Mignot observed that the brains of
narcoleptic dogs had more than the usual number of receptors for the
neurotransmitters acetylcholine, dopamine and norepinephrine and higher levels
of some of the neurotransmitters themselves, changes identical to those Aldrich
(20) later noted human narcoleptic brains.
Given that narcolepsy is not progressive but chronic—i.e. after the
establishment of symptoms, narcoleptics do not deteriorate or improve—
pathologists may have been focusing their efforts on the wrong stage of the
disease's progression. This suggested that the damage might occur during a
(25) short time, roughly during the period in which a patient first develops signs of
the illness. Debris left over from degenerative processes that occurred at the
age of 20 would be removed by the brain's support cells long before most
patients died, and any remaining clues would be obscured by the normal
degeneration of aging. As a loss of neurons would be undetectable unless the
(30) dead cells were concentrated in a particular area, as in Parkinson's disease, or
unless many neurons died, as in Alzheimer's disease, I therefore examined the
brains of narcoleptic dogs shortly after their symptoms had begun, and found
clear evidence that neurons in certain areas of the dogs' brains were
degenerating between one and two months of age, just before and during the
(35) onset of symptoms. Evidence of the degeneration largely disappeared by the
time the dogs were six months old. At this moment, all we can give patients are
drugs to treat narcolepsy's symptoms, even though this research promises the
definite potential of a cure.
In the passage, the author is primarily concerned with
A．presenting a hypothesis and describing compelling evidence in support of it
B．raising a question and describing an important discovery that led to an answer
C．showing that a certain autoimmune disease cannot yet be treated effectively with drugs
D．explaining what evidence exists for an autoimmune cause for narcolepsy
E．discussing the importance of research on animals for the study of human disease
Text 3
Under certain circumstances, the human body must cope with gases at greater-than-normal atmospheric pressure. For example, gas pressures increase rapidly during a dive made with scuba gear because the breathing equipment allows divers to stay underwater longer and dive deeper.
The pressure exerted on the human body increases by 1 atmosphere for every 10 meters of depth in seawater, so that at 30 meters in seawater a diver is exposed to a pressure of about 4 atmospheres. The pressure of the gases being breathed must equal the external pressure applied to the body, otherwise breathing is very difficult. Therefore all of the gases in the air breathed by a scuba diver at 40 meters are present at five times their usual pressure. Nitrogen, which composes 80 per cent of the air we breathe, usually causes a balmy feeling of well-being at this pressure. At a depth of 5 atmospheres, nitrogen causes symptoms resembling alcohol intoxication, known as nitrogen narcosis. Nitrogen narcosis apparently results from a direct effect on the brain of the large amounts of nitrogen cause under these pressurized helium does not exert a similar narcotic effect.
As a scuba diver descends, the pressure of nitrogen in the lungs increases. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues. The reverse occurs when the diver surfaces; the nitrogen pressure in the lungs falls and the nitrogen diffuses from the tissues into the blood, and from the blood into the lungs. If the return to the surface is too rapid, nitrogen in the tissues and blood cannot diffuse out rapidly enough and nitrogen bubbles are formed. They can cause severe pains, particularly around the joints.
Another complication may result if the breath is held during ascent. During ascent from a depth of 10 meters, the volume of air in the lungs will double because the air pressure at the surface is only half of what it was at 10 meters. This change in volume may cause the lungs to distend and even rupture. This condition is called air embolism. To avoid this event, a diver must ascend slowly, never at a rate exceeding the rise of the exhaled air bubbles, and must exhale during as- cent.
31. What does the passage mainly discuss？
A) The equipment divers use.
B) The effects of pressure on gases in the human body.
C) How to prepare for a deep dive.
D) The symptoms of nitrogen bubbles in the bloodstream.
警告：系统检测到您的账号存在安全风险
为了保护您的账号安全，请在“简答题”公众号进行验证，点击“官网服务”-“账号验证”后输入验证码“”完成验证，验证成功后方可继续查看答案！
