The questions might be hilarious, intentionally (or not).

I would ask what is funny about the question. This isn't guaranteed to get an answer as sometimes for various reasons people don't want to are can't articulate why something is funny, but it seems to be a good place to start.

  Or you could ask some other people about the questions, and see if any of them think they are funny.

  I think it would probably be okay to share some examples of the questions here.

If the laughing students are not actually laughing out of amusement, then I would first get that agreed on by them, and then ask why they are laughing, and see what they say. If they say, "no reason", then explain calmly and respectfully (kindly, if that is your preference) that you are finding it difficult to teach when they are laughing, and that you would appreciate it if they would not laugh while another student is asking a serious question.

By treating them with respect, you increase the chance that they will treat you with respect.

If this doesn't work, then you can either try again, asking whether or not they are willing to agree to stop laughing when other students are asking serious questions. If they say no, then you can ask why not, or if you don't care why not, explain that they will be kicked out of your class or whatever if they don't agree to it.

That's what I'd like to think I would do.

The questions might (intentionally or unintentionally) be hilarious.

I would ask what is funny about the question. This isn't guaranteed to get an answer as sometimes for various reasons people don't want to or can't articulate why something is funny, but it seems to be a good place to start. Or you could ask some other people about the questions, and see if any of them think they are funny. I think it would probably be okay to share some examples of the questions here.

If the laughing students are not actually laughing out of amusement, then I would first get that agreed on, and then ask why them they are laughing. If they say, "no reason", then explain calmly and respectfully (kindly, if that is your preference) that you are finding it difficult to teach when they are laughing, and that you would appreciate it if they would not laugh while another student is asking a you a serious question.

By treating them with respect, you increase the chance that they will treat you with respect.

If this doesn't work, then you can try again, asking whether or not they are willing to agree to stop laughing when other students are asking serious questions. If they say no, then you can ask why not, or if you don't care why not, explain that they will be kicked out of your class or whatever if they don't agree to it.

That's what I'd like to think I would do.