John's parents thought that it would be good for his health if he（ ）out of school for the rest of the year.
A、
stays
B、
stayed
C、
has stayed
D、
had stayed
【正确答案】：B
【题目解析】：
本题考查的是虚拟语气，if表示如果，主句为would do，且是对将来发生的事情的虚拟，选B。句意：约翰的父母认为，如果他不在学校度过剩下的一年，那将对他的健康会有好处。
对将来虚拟，形式为，if would do, did/should do/were to do.