浓硫酸和20%的稀硫酸，在实验室中敞口放置．它们的溶液质量和放置天数的关系如图，分析a、b曲线变化的原因是（　　）

A．a升华、b冷凝

B．a蒸发、b吸水

C．a蒸发、b潮解

D．a冷凝、b吸水

---.Don’t you think it necessary that he ____to Miami but to New York?

----I agree , but the problem is _____he has refused to.

A．will not be sent ; that

B．not be sent ;that

C．should not be sent; what

D．should not send; what