You had better found the difference between grade C and grade D by now, unless you're a total moron.
In the future, we will be super tough graders on your edges. If me or another professor demands a grade C edge, make sure you produce one.
In fact, just to hammer this point home, start another tabata and give me at least 8 grade C edges. Should you feel the cum flowing up your shaft during any of these, pay close attention. You may already be stumbling into grade B territory. Stay away from that, though, let's not get ahead of ourselves. Start now. (She watches you intensely as you edge)