Many teens don't get enough sleep because they have too much homework to do which them u

问题补充：

Many teens don get enough sleep because they have too much homework to do, which them up at night.

A. makes

B. breaks

C. turns

D. keeps

答案：

A. makes

B. breaks

C. turns

(答案→)D. keeps

解析：答案：D考查动词短语的辨析。keep sb. up 指“使某人熬夜”。