You Are at the Office and One of Your Coworkers

You are at the office and one of your coworkers, who you only know casually, makes eye contact with you, stares you down, and dashes past you. Assuming you are in the United States, what is your likely reaction?

A) You ignore the man…he means nothing to you
B) You ignore the man….he is obviously crazy
C) You become alarmed…he is obviously crazy
D) You become alarmed…you might have somehow offended him
E) You become angry…he should have said hello