①理清楚结构，什么是插入语什么是修饰
②which要离被修饰的noun越近越好

A选项：be wetter than usual, 固定搭配，所以was多余；同时选项末尾which指代不明确；
C选项：which指代不清楚；be wetter than usual, 固定搭配
D选项：be wetter than usual, 固定搭配,usually❌；
E选项：than usual,现在分词having been colder修饰analysts,语意❌

1. DE：being colder, having been colder, 修饰analysts,错误。D，usually（副词）和前面的colder（形容词）不平行
2. C：usually错误同D，which指代regions，错误
3. A： was usual，was多余；which指代不清

A/B纠结很久，把A中colder and wetter than was usual in some regions当成插入语（同位语），认为后面which从句做weather的定语，所以选了A；B选项中slowing引导的伴随没有动词让它修饰啊。