如果必要的话，我可以乘汽车去。

I can take the car if necessary.

《牛津词典》

如果必要，我们可用铝代替钢。

If necessary, we can use aluminum instead of steel.

youdao

如果必要，我们可用铝代钢。

If necessary, we can use aluminium instead of steel.

《新英汉大辞典》

Again, we reserve the right to move people around if we have to, just to balance load, but we want you to find something that fits your schedule rather than ours.

再说一遍，如果必要的话,我们保留转移你们的权利，只是为了平衡每节课的人数，但是我们希望你们能找到,比适合我们更适合你们时间安排的课时。

麻省理工公开课 - 计算机科学及编程导论课程节选

As completely as was possible and is necessary, would you choose to do it?

如果完全可能而且必要，你会这样做吗？

麻省理工公开课 - 媒体、教育、市场课程节选

So if you find yourself getting most of these answers correct, then don't take this course.

因此如果你发现你能够答对大部分问题,那么就没必要上这门课了

耶鲁公开课 - 聆听音乐课程节选