Parasites, which are smaller than their hosts, include ______.

A、Immune evasion

B、Immunosuppression

C、Sterilizing immunity

D、Mutation changes the antigenicity or immunogenicity of a parasite

What is not one of the bad effects of malaria？

A．The malaria parasites will grow and divide in the kidney.

B．The red blood cells will then be invaded by the parasites which reproduce thousands of times later.

C．The parasites cause a person' s body temperature to rise.

D．People with malaria may suffer kidney failure or loss of red blood cells.

unt them for food. Sometimes, however, two kinds of animals come together in a partnership which is good for both of them. You may see some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites(寄生虫)on sheep. The sheep al- low the birds to do so because they move the cause of discomfort. So although they can live without each other, they do batter together.

Sometimes an animal has a plant partner. The relationship develops until the two partners can- not five without each other. This is so in the corals (珊瑚) of the sea. In their skins there are tiny plants which act as "dustmen", taking some of the waste products from the corals and giving in mturn oxygen(氧气) which the animal needs to breathe. If the plants are killed, or are even prevented from receiving light so that they cannot live normally, the corals will die.

Some birds like to sit on a sheep because______.

A．they can eat its parasites

B．they enjoy traveling with the sheep

C．they depend on the sheep for existence

D．they find the position most comfortable

m for food. Sometimes, however, two kinds of animals come together in a partnership(伙伴关系) which does good to both of them. You may have noticed some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in parasites(寄生虫) on sheep. The sheep allow the birds to do so because they remove the cause of discomfort. So although they can manage without each other, they do better together.

Sometimes an animal has a plant partner. The relationship develops until the two partners cannot manage without each other. This is so in the corals (珊瑚) of the sea. In their skins they have tiny plants which act as "dustman", taking some of the waste products from the coral and giving in return oxygen which the animal needs to breathe. If the plants are killed, or are even prevented from light so that they cannot live normally, the corals will die.

Some birds like to sit on a sheep because ______.

A．they can eat its parasites

B．they depend on the sheep for existence

C．they enjoy travelling with the sheep

D．they find the position most comfortable

B

Most of the animals have little connection with animals of a different kind, unless they hunt them for food. Sometimes, however. two kinds of animals.come together in a partnership which is good for both of them. You may see some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites(寄生虫)on sheep. The sheep allow the birds to do so because they move the cause of discomfort. So although they can live without each other, they do better together.

Sometimes an animal has a plant partner. The relationship develops until the two partners cannot live without each other. This is so in the corals(珊瑚) of the sea. In their skins there are tiny plants which act as "dustmen" , taking some of the waste products from the corals and giving in return oxygen(氧气) which the animal needs to breathe. If the plants are killed, or are even prevented from receiving light so that they cannot live normally, the corals will die.

60. Some birds like to sit on a sheep because_____

[ A] they can eat its parasites

[ B ] they enjoy traveling with the sheep

[C] they depend on the sheep for existence

[ D] they find the position most comfortable

【单选题】A 7-year-old girl has 1 1-month history of foul-smelling diarrhea. Upon further inquiry, the frequency seems to be 4-6 stools per day. She has also had trouble seeing at night in the past2 weeks. Her WBC count is normal. Physical examination is entirely normal. Examination of a stool sample reveals that it is bulky and greasy. Analysis does not reveal any pathogenic microorganisms or parasites but confirms the presence of fats. Further evaluation of this patient would likely reveal which of the following conditions？

A、Lactose intolerance

B、Biliary insufficiency

C、Ileal disease

D、Diabetes

E、Giardiasis

听力原文： Most animals have little connection with animals of a different kind, / unless they hunt them for food. / Sometimes, however, two kinds of animals come together in a partnership / which docs good to both of them. I You may have noticed some birds sitting on the backs of sheep. /This is not because they want a ride, / but because they find easy food in the parasites on sheep. / The sheep allow the birds to do so/ because they remove the cause of discomfort. / So although they can manage without each other, they do better together. / Sometimes an animal has a plant partner. / The relationship develops until the two partners cannot manage without each other. / This is so in the corals of the sea. / In their skins they have tiny plants which act as" dustman", / taking some of the waste products from the corals / and giving in return oxygen which the animal needs to breathe. / If the plants are killed, / or are even prevented from light so that they cannot live normally, / the corals will die.

(1)

unt them for food. Sometimes, however, two kinds of animals come together in a partnership (伙伴关系)which is good for both of them. You may see some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites (寄生虫)on sheep. The sheep allow the birds to do so because they move the cause of discomfort. So although they can live without each other, they do better together.

Sometimes an animal has a plant partner. The relationship develops until the two partners can not live without each other. This is so in the corals(珊瑚)of the sea. In their skins there are tiny plants which act as "dustmen", taking some of the waste products from the corals and giving in return oxygen which the animal needs to breathe. If the plants are killed, or are even prevented from receiving light so that they cannot live normally, the corals will die.

Some birds like to sit on a sheep because ______.

A．they can eat its parasites.

B．they enjoy travelling with the sheep

C．they depend on the sheep for existence

D．they find the position most comfortable

ds on the existence of other organisms. This interdependence is sometimes subtle, sometimes obvious. Perhaps the most straightforward dependence of one species on another occurs with parasites, organisms that live on or in other living things and derive nutrients directly from them. The parasitic way of life is widespread. A multitude of microorganisms (including viruses and bacteria) and an army of invertebrates——or creatures lacking a spinal column (including crustaceans, insects, and many different types of worms)—— make their livings directly at the expense of other creatures. In the face of this onslaught, living things have evolved a variety of defense mechanisms for protecting their bodies from invasion by other organisms.

Certain fungi and even some kinds of bacteria secrete substances known as antibiotics into their environment. These substances are capable of killing or inhibiting the growth of various kinds of bacteria that also occupy the area, thereby eliminating or reducing the competition for nutrients. The same principle is used in defense against invaders in other groups of organisms. For example, when attacked by diseasecausing fungi or bacteria, many kinds of plants produce chemicals that help to ward off the invaders.

Members of the animal kingdom have developed a variety of defense mechanisms for dealing with parasites. Although these mechanisms vary considerably, all major groups of animals are capable of detecting and reacting to the presence of "foreign" cells. In fact, throughout the animal kingdom, from sponges to certain types of worms, shellfish, and all vertebrates (creatures possessing a spinal column), there is evidence that transplants of cells or fragments of tissues into an animal are accepted only if they come from genetically compatible or closely related individuals.

The ability to distinguish between "self" and "nonself", while present in all animals, is roost efficient among vertebrates, which have developed an immune system as their defense mechanism. The immune system recognizes and takes action against foreign invaders and transplanted tissues that are treated as foreign cells.

What does the passage mainly discuss？

A．How parasites reproduce.

B．How organisms react to invaders.

C．How antibiotics work to cure disease.

D．How the immune system of vertebrates developed.