Now that there are still some problems remaining we have to work extra hours tonight.A.

问题补充：

Now that there are still some problems remaining , we have to work extra hours tonight.

A. solved

B. solving

C. to be solved

D. to solve

答案：

A. solved

B. solving

(答案→)C. to be solved

D. to solve

解析：考查remain的用法:句意：现在还有很多问题有待去解决，我们今晚要加班了。Remain to be done有待去做，选C。