大全113：比较问题，又糊涂了

113. Analysts blamed May’s sluggish retail sales on unexciting merchandise as well as the weather, colder and wetter than was usual in some regions, which slowed sales of barbecue grills and lawn furniture.

(A) colder and wetter than was usual in some regions, which slowed

(B) which was colder and wetter than usual in some regions, slowing

(C) since it was colder and wetter than usually in some regions, which slowed

(D) being colder and wetter than usually in some regions, slowing（B）

(E) having been colder and wetter than was usual in some regions and slowed

我记得在比较时间状语的时候，不是应该要把比较的部分补全吗？比如：United States have more population than 100 years ago. 就不对，应该说United States have more population than it had 100 years ago. 为什么这里就可以直接说then ususal?

有点糊涂了，请NN指点……

1.than usual是个固定的省略形式,另外好像还有两个,在白勇的书上看到过,具体不记得了,一时也找不到在哪.

2.比较从句是可以省略一些重复成份的,比如,主语相同可以省略,be动词相同可以省略,主谓如果都相同可以一起省略只保留介词短语和副词.等等.就算不是固定省略形式,这里的省略也符合以上规则啊

还是WHICH 问题,不是"句子,WHICH"的形式是错的吗.?谢谢!!!