The children went home from the grammar school, their lessons ______ for the day.

A．finishing

B．finished

C．had finished

D．had been finished

从100升纯酒精中取出1升倒入100升水中，混合均匀后取出1升倒回纯酒精。若这时酒精中含水的比是x，水中含酒精的比是y，则有（）。

A．x＞y

B．x＜y

C．x=y

D．x≥y

E．无法判断