How can I prevent submission if certain fields are not entered?

I am building a form to let people apply to our program. There are 3 essay questions at the end. They must answer at least one of them (their choice of which one). Then there is the "Submit" button.  How can I set up a condition to confirm that at least one question has been answered and, if not,  then put up an error message and prevent the "Submit" from taking place until they do make an entry? In other words: "If Q1 is blank AND Q2 is blank AND Q3 is blank send error message, ELSE allow "submit".

Hello,

You could use "Required" option in form builder for the fields that needs to be filled in order form to be submitted. 

You could also use conditional required fields. Please have a look at following article for that: https://www.jotform.com/help/367-How-to-Make-a-Field-Required-Based-on-User-s-Answer

Please let us know if that won't help you.

Regards.

Thanks to both of you for the answers and links.

I am familiar with and have used conditionals a number of times.

This is not a situation where a field is required based on a previous answer (like: if they chose "no" in a select field, I could open a box to say "Why not?".

This is where they have to answer ANY one of several optional fields.

But...looking at the info in the links provided, I learned that I can make the "Submit" button "Show" or "Hide" based on a condition; did not realize this was an option!

So I am able to do that to solve my issue!  Here is my test form with that logic (on page 2):

https://form.jotform.com/72975162109157