Here, if Professor A says something is obvious, it means that if you go home and think about it for the rest of the afternoon, you will probably see that it is true.
If Professor L says something is obvious, it means that if you go off and spend the rest of your life considering it, the day might eventually come when you see that it is true.
If Professor W says something is obvious, it means that the class has known about it for the last two weeks.
If Professor F says something is obvious, it means that it is probably false.