Not done ! (no warning)

It's a little bit annoying for me that there is no warning when you click on “SEND”, indicating that some parts are not done.
Most of time, it is not your willing. You can be distract for any reason (eg. a phone call during your lesson). Or you can miss a question.
I believe it would be a slender effort for you to check this point and a great help for your students (aka customers). Thanking you in advance.