一题( )________a pig on the road ,the bus was stoppedA.The dri

1.until的后面可以接具体的时间,也可以
接一个时间状语从句.它既可以用于肯定句
中,又可以用于否定句中,但用法不同.
一、用于肯定句中,意思是“到…为止”,表示动作一直持续到表示的时间为止.主句的动词必须是延续性动词.eg:I will wait here until half past four.
He worked in the office until the cleaner came in.
二、后面的从句中不能用将来时,如果要表示将来的动作或状态,则用一般现在时代替.eg:He will stay here until his mother comes back.
They will study at the school until their parents come to take them home.
三、until用于否定句中,意思是“直到…才”,表示动作从until表示的时间才开始,主句动词延续性、非延续性均可.
eg:I didn’t go to bed until 12 last night.
I won’t come back until my mother asks me.
He doesn’t do his homework until his father comes back every day.
2.首先句子中没有连词,所以present之后用非谓语,其次present是被安放的,属于被动态,所以用set
3.前半句由于是假设,所以是虚拟语态,后半句是现实,因此不需虚拟语气,用一般的状态即可.