His uncle gave him books to read, but after a page or two he would put __book down and pick up__ new one.

A．the,/

B．a; a

C．a; the

D．the; a

如图所示，一定质量的空气被水银封闭在静置于竖直平面内的U型玻璃管中，右管上端开口且足够长，右管内水银面比左管内水银面低Δh，能使Δh变大的原因是

A.环境温度降低或者大气压强增大

B.环境温度升高或者大气压强减小

C.环境温度升高或者U型玻璃管自由下落

D.环境温度升高或者沿管壁向右管内加水银