If I let you have the book, you must read it carefully.

如果我给你这本书，你必须仔细读。

If I do go to Tainan, what is the best train to take?

假如我要到台南，哪一班火车最方便？

He asked if he might go.

他询问他是否可去。

If the answer is correct, the work is not neatly done.

答案虽无误，但做得不俐落。

If I have any question, I will come to you.

我若有问题将向你请教。

If I have doubt, I inquire.

我有疑问就询问。

The ifs of life are many.

人生之疑问颇多。