问题

What’s up? You look worried.Well,I_____on the problem for 5 hours but I haven’t got a single clue

A:have worked
B:worked
C:will work
D:have been working

正确答案是：

同类题型

Lisa is a little poor at Chinese. I think she needs _____ it every day.

Is this a map — Yes,_____.

下列各句中．没有语病的一句是

I‘d like a pen which _________ well.—Will this one _________?

The plane will arrive ______ Shanghai ______ 8:00 _____ the evening of September 10.