He was seriously injured last week and that’s he didn’t participate in the competition. A

问题补充：

He was seriously injured last week and that’s he didn’t participate in the competition.

A. when

B. how

C. why

D. what

答案：

A. when

B. how

(答案→)C. why

D. what

解析：句意：上周他受伤严重，这就是他为什么不能参加比赛的原因。That’s why….这就是为什么。When什么时候，why为什么，what什么，都不符合句意，所以选C。