Only after they had discussed the matter for several hours an agreement.
A. they reached
B. do they reach
C. they reach
D. did they reach
网友回答
A. they reached
B. do they reach
C. they reach
(答案→)D. did they reach
解析：考查倒装句。当only放在句首，且强调的是状语的时候，后面的主句使用部分倒装的形式。本题only放在句首，强调的是时间状语after they had discussed the matter for several hours,故后面使用部分倒装的形式，因为时态had discussed说明这里使用一般过去时。句意：只有当他们讨论了几个小时以后，他们才达成了一致的意见。故D正确。