the kind of question can be ignored?

In English, do we have any structure (I mean grammar) in question let the listeners know that they do not need to answer or the answer from them is not really important ?

What’s the way to give this kind of question ?

I think what you mean is a rhetorical question. But it is not the grammar that makes it rhetoric but instead the context. But I think you can add something like “after all”, or “by any chance” to indicate it is rhetoric. For example “Are you crazy?” is a rhetorical question basically calling someone crazy. The context should make that clear and it is not intended to be answered but if it is isolated then it is not clear what the original intention is. If you wanted to make sure that this is clearly rhetorical then you could say " By any chance are you crazy?". Isolated this more clearly looks like a rhetorical question.

Waiyin, the main difference is in tone. The rhetorical question usually falls in end tone where the real question rises, and vice versa.

Thank you for your help. Mr Mister Micawber.