Look! There are so many mistakes in your composition. You have fixed full attention on it

问题补充：

Look! There are so many mistakes in your composition. You have fixed full attention on it.

A. can

B. should

C. need

D. might

答案：

A. can

(答案→)B. should

C. need

D. might

解析：选B考查情态动词。句意：看！你的作文里有那么多的错误。你本应该把所有的注意力都集中在它上面的。表示“本应该做但实际上没有做”应该用should have done结构，故选B。