用look构成的短语的适当形式填空

1.____on my childhood, I am always feeling happy.

2.We should____ the ones who have more knowledge than ourselves.

3.The little boy____ the old couple as his parents.

4. We should learn to____ a problem from all sides.

5. The baby is____ by his parents carefully.

6. I'm____ his reply.

月经的发生是由于（）

A.雌激素急剧减少

B.孕激素急剧减少

C.雌、孕激素均急剧减少

D.FSH、LH急剧减少

E.促性腺激素急剧减少