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
网友回答
A. they reached
(答案→)B. did they reach
C. they reach
D. do they reach
解析：考查only的倒装。Only倒装要符合两个条件：only放在句首；后面强调状语；本题都符合，only放在了句首，强调的是时间状语after they had discussed the matter for several hours，故使用部分倒装的形式。根据时态，可知使用过去时，排除D项。