6.No sooner ___ at the Grand Theatre than it started to rain.A. would they arriveB. had they arrivedC. did they arriveD. were they to arrive

本题考查“no sooner...than...”结构的用法。解题核心在于掌握以下两点：

1. “no sooner”引导的从句需用过去完成时，且必须将助动词“had”提前至句首构成倒装；
2. “than”引导的主句用一般过去时，表示两个动作先后发生。

选项分析

A. would they arrive

• 错误原因：“would”表示过去将来时，与“no sooner”要求的过去完成时不符。

B. had they arrived

• 正确原因：
  1. “had”提前构成倒装，符合“no sooner”句式要求；
  2. “arrived”为过去分词，与“had”构成过去完成时，表示“到达”动作先于“下雨”发生。

C. did they arrive

• 错误原因：“did”用于过去式的强调或疑问，但此处需用过去完成时，且未体现动作的先后顺序。

D. were they to arrive

• 错误原因：“were to”表示推测或计划，表示将来时，与“no sooner”要求的已完成动作矛盾。