________ that this region was so rich in natural resources.A. Little he knewB. Little did he knowC. Little he did knowD. Little he had known

本题考查倒装句的用法，特别是以否定词little开头的倒装结构。关键点在于：

1. 否定词位于句首时，句子需要部分倒装（即助动词/系动词提前到主语前）。
2. 动词的时态需与上下文一致。原句中从句用过去时was，主句也需用对应时态。

选项分析

A. Little he knew

• 错误：未使用倒装结构。knew是动词过去式，但倒装时需用助动词did提前，结构应为Little did he know。

B. Little did he know

• 正确：符合倒装规则。did作为助动词提前，主语he后接动词原形know，时态为过去式，与从句was一致。

C. Little he did know

• 错误：did位置错误。倒装时did应置于主语前，正确形式为Little did he know。

D. Little he had known

• 错误：时态不匹配。从句用过去时was，主句若用过去完成时had known会导致时态矛盾。