How can I make a form which shows only if I check a specific option?

Hello,

I’m making a contact form for my clients’ site, and I can’t see an option which will allow me to do something like this:

I have a question X, which has option Yes and No. If user chooses Yes, nothing changes, but if he chooses No, three additional fields will be available. Is there an option to do it without changing something in PHP code?