解释：

... the rules of basketball (or your favourite game or sport).

... how space travel can be of benefit in the future.

... why crime occurs in modern cities.

... the need for an international language.

... why you chose your particular field of study.

说明：

... a folk story in your culture that has significance.

... the plot of a good book you have read recently.

建议你用的字句....

Could you please rephrase that question/topic?

I'm not exactly sure what you mean ...

I'm not exactly sure how to answer that question, but (perhaps) ...

That's a rather difficult question, but (maybe) ...

I'm sorry, but I don't know much about ...

However, it might be possible that ...

Maybe I can answer your question by telling you about a personal experience I had.

That's an interesting question ...

Let me see. Well, I suppose that ...

Well, I think there are 2 (or 3 or more) reasons:

First, ... Second, ... Finally, ...

In my opinion there are three ways of looking at it:

First of all, ... Next, ... Then, ...

Have I given you enough information?

Would you like me to tell you more about ...?

Is that all you'd like to know?

I'm afraid that's about as much as I know.

I think that's about it.

I can't think of anything else right now ...