第一步:观察空格前是否有名词,判断是哪种从句类型。空格前有相应名词的多为定语从句或同位语从句,空格前没有相应名词的多为状语从句或名词性从句(同位语从句除外)。如:①We reached what used to be an old factory.②We reached the place which/that used to be anold factory. The first step: to observe whether there are nouns before the box to determine what type of clause. Most of the corresponding nouns before a space are attributive clauses or appositive clauses, and there are mostly no adverbs or adverbs of nominal nouns before the spaces (except for the homophonic clauses). Such as: ① We reached what used to be an old factory. ②We reached the place which / that used to be anold factory.