Only after they had discussed the matter for several hours a decision.A. they reachedB. di

问题补充：

Only after they had discussed the matter for several hours a decision.

A. they reached

B. did they reach

C. they reach

D. do they reach

答案：

A. they reached

(答案→)B. did they reach

C. they reach

D. do they reach

解析：考查倒装句。Only的倒装有两个条件：only放在句首，且强调状语时，后面使用部分倒装。本题两个条件都符合。句意：只有在他们讨论这个问题几个小时以后他们才得出结论。