1) I will call you as soon as I get home.
我一到家我就给你电话.(主句用一般将来时,从句用一般现在时.)
2) If it rains , the math will be put off the next Friday.
如果天下雨的话,比赛将推迟到下周五.(主句用将来时,从句用一般现在时)
3)I was doing homework when he came in .
主句用现在或过去进行时,从句用一般现在时或一般过去时.