状语从句，此用法与if引导的条件状语从句相同，主句用-----时从句用------时

主句用一般将来时，从句用一般现在时 主将从现 记住哦

时间状语从句和条件状语从句中，其谓语动词一般不用将来时，而用一般现在时代替一般将来时，一般过去时代替过去将来时，现在完成时代替将来完成时。 其他部分不变~
如 The bell is rung if there is a fire.
You will be late unless you leave immediately.
The WTO can't live up to its name if it doesn's include a country that is home to one fifth of mankind.