How to hide submit button

How can I avoid these "submit " buttons on my screen when doing exercises, it really disturbs me.

If you just do “Kernel → Restart and Clear Output”, they will go away. But also you’ll then need to rerun the cells in the notebook again with “Cell → Run All” or “Cell → Run All Above”. When you do that you may get another one of those bogus submit buttons. They may look annoying, but they really don’t do any harm.