A Physics Professor Pushes Against a Stationary Wall, "Working" Up

A physics professor pushes against a stationary wall, "working" up a sweat. Is he doing any actual physical work on the wall?

A) No-- it's a law of nature that physics profs never do any actual work.
B) No, because the wall is not moving.
C) Yes, because his arm muscles are moving other muscles through a distance.
D) Yes, because he is exerting a force against the wall during a period of time.
E) No, because the force by his hands against the wall is balanced by the force by the wall pushing back.