如果他们不干这个工作，我们就需要一个应变的方案。

We need a fallback position if they won't do the job.

《牛津词典》

如果他们不能及时给我们拿来，我们就只好将就了。

If they can't get it to us in time, we'll just have to do without.

《牛津词典》

如果他们对我们方向采取了任何行动的话，我们也就会进行了反制。

If they had made any sort of move that was in our direction we would have made a countermove already.

《柯林斯英汉双解大词典》

And, if we wanted to try to fit, say, hydrogen, into this scheme that we have, we have to do what?

如果我们想要让他们符合我们的原理比如氢气，我们需要怎样？

麻省理工公开课 - 固态化学导论课程节选

Oh--but if you can meet with our teaching fellows over there, they're gonna ask the legal department to see you next so Alright, I think we're all set.

哦，但是如果你遇到我们的助教，他们将让法务部看下你,我想我们大家准备好了。

哈佛公开课 - 计算机科学课程节选

You know from experience if you've ever mixed them to make salad dressing, they don't mix too well. And you may know that if you heat them up, they mix much better.

经验告诉我们,你无法把它们混合做成色拉酱调料，他们不会很好的混合，但是你也知道,如果我们把他们加热，就能够混合的更好。

麻省理工公开课 - 热力学与动力学课程节选