在下列各句的空格内填上一个适当的单词，该词的首字母已给出。

1. I can't hear you. Can you read it a_______?

2. If you work hard, you will s________ in the end.

3. His mother often teaches him the i________ of working hard.

4. Peter f______ his math test last time. He was sad.

5. Though he is much too s_______, he tries his best to keep awake.

肿瘤经照射后一段时间，细胞的乏氧水平可低于照射前，是由于发生了（）。

A.放射损伤修复

B.细胞周期再分布

C.乏氧细胞再氧合

D.再群体化

E.以上均不对