题目内容
Once harm ______ to the environment, it takes years to have the system recovered.
A. does B. is done C. will be done D. be done
B
考查被动语态。此处harm是不可数名词,用单数。句意:一旦对环境造成伤害,它需要花费多年的时间回复生态系统。
Once harm ______ to the environment, it takes years to have the system recovered.
A.does | B.is done | C.will be done | D.be done |