_______the danger from enemy attacks, people had to face the lack of food, clothing, fuel and almost everything.

A．As far as

B．As long as

C．As well as

D．As soon as

如图2-38所示的牛顿环实验装置中，用单色光垂直照射，当凸透镜垂直向上缓缓平移而远离平板玻璃时，则可以观察到这些环状干涉条纹（）。

A.向中心收缩

B.向外扩张

C.向右平移

D.静止不动