The Chinese began using commodity currency in the shape of knives or other tools in_______
A、proceed
B、gaze
C、lodge
D、approve
In this cam mechanism, shape of cam is a circle with geometric center O and radius R=30mm. Eccentricity, roller,offset. Try to label following items on figure: (1) Follower rise h and radius of cam base circle, (2) Cam angle for rise,cam angle for outer dwell, cam angle for returnand cam angle for inner dwell, (3) Maximum pressure angleand its location, (4) Cam rotating angleand follower displacementwhen contact point moves from B to C. (5) Pressure angleon point C.
1. In tomato, the round fruit (R) is dominant to pear shape(r), while the single flower (B) is dominant to multiple flowers (b). Now using double homozygotes as parents, we get F1 generation. F1 testcrosses with the double recessive homozygotes, the following progenies were obtained: Round, single flower 34, Round, multiple flowers 214 Pear, single flower 216, Pear, multiple flowers 36 Question: (1) Are gene R and B linked? (2) What are the genotypes of the two homozygous parents? (3) If the two genes linked, what is their genetic distance? If the two genes not linked, please write out the genotype of F1.
A、by sample
B、by specification
C、by grade
D、by name of origin
A、only about 1 percent difference in DNA
B、one of kind, not of degree
C、spoken language
D、Very small biological difference
When a good reader is at work, he does not look at letters, nor even at words, one by one, however quickly; he takes in the meaning of two, three, or four words at a time, in a single moment. Watch carefully the eyes of a person who is reading, and it will be seen that they do not travel smoothly along the lines of print, but they move by jumps separated by very short stops. The eyes of a very good reader move quickly, taking long jumps and making very short halts (停顿); the eyes of a poor reader move more slowly, taking only short jumps and stopping longer at each halt. Some- times, when he meets a difficulty, he even goes backwards to see again what has already been looked at once.
The teacher’s task is therefore clear: it is to train his pupils to take in several words at a glance (one "eye jump" ) and remove the necessity for going backwards to read something a second time.
This shows at once that letter-by-letter, or syllable-by-syllable (音节), or word-by-word reading, with the finger pointing to the word, carefully fixing each one in turn, is wrong, It is wrong because such a method ties the pupil’s eye down to a very short jump. Moreover, a very short jump is too short to provide any meaning or sense; and it will be found that having struggled with three or four words separately, the pupil has to look at them again, all together and in one group, in order to get the meaning of the whole phrase.
Which of the following is closest in meaning to the first paragraph?
A.Pupils should be trained to reach quickly the stage of reading without having to concentrate on the separate symbols.
B.Pupils should look at each printed symbol for its meaning as well as for its shape.
C.Teachers should help their pupils avoid looking at the shape of the printed symbols.
D.Teachers should tell their pupils the different stages of their study.
A、the total volume of new air entering the alveoli each minute..
B、the amount of air inhaled into or exhaled from the lung in one quiet respiratory cycle.
C、the amount of air inhaled into or exhaled from the lung in one minute in quiet respiration.
D、the total volume of air inhaled forcefully in one respiratiory cycle.
E、the total volume of air in lung at the end of quite expiration.
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