I should be happy to go with you.如果能与你一起去，我将很高兴。
(=If should be happy if I could go with you.)
To have studied harder,you would have passed the examination.
你学习更用功些，你早就考及格了 。 （=If you have studied harder, you....)
Born in better times ， he would have been a scholar.
(=If he had been born in better times ， he…)
Failing this time ， what would you do?
（ = If you failed this time ， what…)
Walking alone in the dark ， Mary would be terrified.
(if Mary walked alone in the dark,she would be terrified.)
Without air， no one could live.没有空气，人就不能活。
(=If there were no air» no one could live.)
But for his help, he would have failed.要不是有他的帮助，他就会失败了
(=If it hadn ，t been for his help，he would have failed.)
A true friend would not have betrayed me.
(=If he had been a true friend ， he would…)
A few hours earlier» and you would have seen the famous writer.
(if you had come a few hours earlier，you...)
I didn ，t know that he was a cheat, or else I wouldn ，t have believed him.
我不知道他是个骗子，不然我也不会相信他了 。(or else = if I had known he was a cheat)
I'm really very busy, otherwise I would certainly go there with you.
我真的是太忙了 ，不然我就会同你一遒去了 。
(otherwise = if I were not so busy)
Anyone who had seen that painting might have taken it for a photo.
(=If anyone had seen that painting • • •)
Don ,t bother to read all these papers. It would take too long.
(=If you read all these papers ， it would take too long.)