—Daviddidn’ttakepartinthevolleyballmatchlastnight.—Yes....

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—David didn’t take part in the volleyball match last night.

— was________he had injured his foot in the training.

A．why B．because

C．whether D．what

B　考查表语从句。根据对话提供的情景，上句“没有参加比赛”是结果，下句“他在训练中脚受伤了”是原因，故用because引导表语从句。That is because...那是因为……，because后接原因；That is why...那是……的原因，why后接结果。