Gustav Works with a Difficult Boss

Gustav works with a difficult boss. His boss is a micromanager, so he often invites her input because he realizes there is little he can do to change her behavior. He often gratuitously complains about her behavior to his coworkers. Even though she is often negative, Gustav remains positive in the way he communicates towards her. Which part of this description shows Gustav maintaining a professional demeanor?

A) His boss is a micromanager.
B) He realizes there is little he can do to change her behavior.
C) He often gratuitously complains about her behavior to his coworkers.
D) Even though she is often negative, Gustav remains positive in the way he communicates towards her.