In the Six Dynasties, Liu Qing, a famous talker, talked a lot, but he also admired people who didn't speak. He was very happy to see Jiang Quan speak very infrequently, saying, "Jiang Quan can't speak, but he can admit it if he can't say it. " Jiang Quan knew that he was not talking, but he knew how to hide. Not everyone knew where his shortcomings were, so that he could talk to countless people. He could talk and love to say that there was some excuse; many people obviously did not speak. I just kept talking about it, and it was always annoying because of its shortcomings. Therefore, it can be said that Jiang Quan was actually very rare in doing so. Which of the following, if true, best supports the above conclusion? ['Being able to speak but not speaking is an extremely rare intelligence.', 'It is a self-knowledge to be silent.', "It can't be said to be an exaggeration.", 'Not speaking is actually a helpless move.']