Question

9. The worried parents found their lost child in        a chemical works (be)

那对焦急的父母在一个曾经是化工厂的地方发现了他们丢失的小孩。

Answer 1

9. what used to be本题考查名词性从句。 in后面所接的是介词宾语从句，从句中缺主语,所以用what引导。若用the place that/which used to be或the place where it used to be亦可。