题干
18. ----- Has Mary finished writing her article ?
----- No, and it _____ before class was over.
A：should be finished
B：should finish
C：should have finished
D：ought to have been finished
答案(点此获取答案解析）
A
Ca2+（aq）+2OH－（aq）．当向悬浊液中加少量生石灰后，若温度保持不变，下列判断正确的是（ ）