---Sorry I’m late for class again.---Is it you stayed up last night?A. whyB. howC. becau

问题补充：

---Sorry, I’m late for class again.

---Is it you stayed up last night?

A. why

B. how

C. because

D. when

答案：

A. why

B. how

(答案→)C. because

D. when

解析：why为什么；how如何，怎样；because因为；when当……时。句意：抱歉，我上课又迟到了。——是因为你昨晚熬夜吗？结合语境可知选Ｃ。