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

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+状语或状语从句位于句首，主谓用部分倒装。故排除A与C。又因为时态应前后一致。故选B。