【题目】Tom hasn't recovered from his knee injury.That's ________we didn't see Tom run in the race.
A.because
B.that
C.why
D.what

【答案】C
【解析】句意：Tom的膝关节还没有康复。那就是我们没有看到他参加比赛的原因。这里构造表语从句，用why指代原因。故选C。