根据句意和汉语注释，写出单词的正确形式。

1. Like many famous scientists, Li Siguang __________ (致力于) himself to the study of science.

2. __________ (医疗的) workers are badly needed in those earthquake-hit areas.

3. I don't think the watch gives you good __________ (价值) for your money.

4. The tourists had no ___________ (选择) but to wait for the next train.

5. How are you going to ___________ (证明) that it is very difficult for giant pandas to survive in the wild?

要制备电镜的半薄切片，可用的组织固定方法是（）

A.中性甲醛液体

B.丙酮

C.可先用戊二醛固定，然后再用锇酸进行二次固定

D.乙醇固定

E.先用甲醛固定，然后再用戊二醛进行二次固定