There uesd to be a lot of chemical plants in the south,but many of them have been closed or are ? b

题目

There uesd to be a lot of chemical plants in the south,but many of them have been closed or are ? be closed. A to B supposed to
说明原因

答案

选A,to be表示将会发生的,supposed to是应该,假设的意思,虽然语法上没有错误,但意思上说不通