The following is missing for the question to be complete:
A. Variation in interpreting information
B. An oversized ego
C. A tendency to judge others' messages
D. Variable skills in communicating effectively
E. An inability to listen with understanding
Answer: B. An oversized ego
Explanation: Anything that prevents us from communicating in terms of exchanging opinions, messages, understanding and observation is a communication barrier. These barriers can be external, therefore sometimes objective, still not always objective though external, and may be internal, therefore, barriers that come from our thoughts, prejudices, feelings, or as in this case JJ's barrier can come from too much ego.
He obviously listened to the advice of his peers until he reached the goal of being promoted to manager, and it seems that was the only reason that he listened to them, not to exchange observations and information but to give the impression of a good associate and thus earn good grades from superiors. When, in his own opinion, he finds himself in the position that he no longer has to do it, that is, to listen and take advice from others or even from his boss, then his true ego, i.e oversized ego, comes to the front.
Since he decided to run the project exclusively the way he thinks best is proof that while he used to take advise from his peers, he did not really appreciate them but did so for practical career reasons. After the promotion, he shows what he really thinks of others and thinks that he can lead the project on his own without having an exchange of views, which of course cannot be the best. Information sharing and observations can often be very useful, sometimes crucial to making good decisions. However, good decisions can be overshadowed by too much ego.