A: I enjoyed the performance very much.
B: Yes, it was really good. I think ________ boy in white was the best actor.
A:a
B:an
C:the
D:/
如图所示,实验装置足以维持实验期间小白鼠的生命活动,瓶口密封,忽略水蒸气和温度变化对实验结果的影响。经数小时实验后,U形管A、B两处的液面会出现下列哪种情况( )