选词组填空（共5小题；每小题2分，满分10分）。

1.While ____________ a knife to cut something, you need to be very careful.

2. After the earthquake, the whole city ____________.

3. Has she _____________ to improve her terrible handwriting?      

4. _____________ get the first prize in the sport meeting, he insists on practicing every day.

5. Ever since he was put into prison, he _____________ a lot of sufferings.

氦氖激光器某一跃迁产生632.8nm谱线，求400K时它的多普勒线宽（）。

A、3.39GHz

B、1.52GHz

C、1.38GHz