英语被动语态的从句的时态,是和主动语态的从句的时态一样吗?例如,The students must finish all tne exercises before school is over.的被动语态中,before school is over要改变时态吗?如果要改,是什么时态?We should turn on the lights when the charity show starts.的被动语态中,when the charity show starts要改变时态吗?如果要改,是什么时态?不难的.这一块老师刚讲,有的问题我还不太明白.