题目

Only after they had discussed the matter for a few hours________a decision. A．they reached  B．did they reach C．they reach  D．do they reach 答案：B　考查倒装结构。句意：只有在他们讨论这个问题好几个小时之后他们才作出决定。only修饰时间状语从句且位于句首时，主句应采用部分倒装的形式。根据状语从句的时态可以确定主句应用一般过去时态。故选B。

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