________I admit the boy has a gift for music,I don't think he will make a good singer.
A:Since
B:While
C:Until
D:Unless
观察鲫鱼时,我们看到鲫鱼的身体呈____ 形,这种体形在它游泳时可以起到减小____ 的作用.
下图是人体部分生理活动示意图,请据图回答: