_ , but they also brought cards for entertainment when they had a picnic in the forest.A. Not only they brought snacks and drinksB. Not only did they bring snacks and drinksC. Not only snacks and drinks they broughtD. Not only they did bring snacks and drinks

本题考查倒装句的用法，特别是not only...but also结构的语序。当not only位于句首时，其后的从句需要部分倒装，即助动词/情态动词/系动词需提前至主语前。解题关键在于：

1. 识别倒装结构：确认not only引导的分句是否符合倒装规则；
2. 排除干扰项：注意主谓位置是否颠倒，以及动词形式是否正确。

选项分析

A. Not only they brought snacks and drinks

• 错误原因：未进行倒装。not only位于句首时，需将助动词did提前至主语前，正确形式应为Not only did they bring...。

B. Not only did they bring snacks and drinks

• 正确原因：符合倒装规则。将助动词did提前至主语they前，构成部分倒装，且动词bring与后文brought时态一致。

C. Not only snacks and drinks they brought

• 错误原因：结构混乱。not only后应接动词短语，而非名词短语snacks and drinks，且未正确倒装。

D. Not only they did bring snacks and drinks

• 错误原因：助动词位置错误。did应置于主语前，正确形式为Not only did they bring...。