用 when或 while填空。

1. I was looking out of the window _________ the teacher asked me.

2. What is he doing _________ his parents came back？

3. Mike was playing games _________ Jack was studying.

4. I was about to fall asleep _________ the baby began to cry.

下图示某高等动物体内细胞分裂的几个时期，下列有关说法正确的是（）

A.甲图中有2个四分体

B.乙图中一定有等位基因存在

C.丙图内可能发生了基因重组

D.丙图表示次级精母细胞