题目

Since he heard of his failure at the examination，Tom ________. A．had been very cast down B．has very cast down C．had very cast down D．has been very cast down   答案： D 此题考查时态和语态。be cast down“使泄气”；since往往与现在完成时连用。句意是：自从他听到他考试失败以后，汤姆就非常沮丧。  

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