词汇与结构There is, of course, a limit to how far the angle of attack can be increased, if a _____ is to be avoided.
A. acceleration
B. stall
C. deceleration
D. failure
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词汇与结构Lift and drag also vary directly with the _____ of the air.
A. concentration
B. density
C. intensity
D. condition
词汇与结构Warm air is less dense than cool air, and _____ air is less dense than dry air.
A. humid
B. wet
C. moist
D. damp
白化病是由隐性基因控制的,如果一对正常夫妇生下了一个有病的女儿和一个正常的儿子,这个儿子如果与患有白化病的女人结婚,婚后生育出患有白化病女孩的几率为 ( )
A. 1/2
B. 1/4
C. 1/6
D. 1/12
基因型为 RrYY 的生物个体自交,产生的后代,其基因型的比例为 ( )
A. 3:1
B. 1:2:1
C. 1:1:1:1
D. 9:3:3:1
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