12.Rising inventories, when unaccompanied correspondingly by increases in sales, can lead to production cutbacks that would hamper economic growth. (A) when unaccompanied correspondingly by increases in sales, can lead (B) when not accompanied by corresponding increases in sales, possibly leads (C) when they were unaccompanied by corresponding sales increases, can lead (D) if not accompanied by correspondingly increased sales, possibly leads (E) if not accompanied by corresponding increases in sales, can lead 答案选E,没有问题。 但是 if not accompanied by corresponding increases in sales, 做什么成分呢?if是连词,引导的却是一个过去分词短语,如果换成when的话,至少是个介词短语。又或者是省略?,因为和主句相同的主语,连着系动词are一起省了?