Please explain which one is correct: 1) The good speaker must possess sincerity, a good platform manner, and have the ability to express his thoughts. 2) Good speakers must possess sincerity, good platform manners, and the ability to express their thoughts. 3) The good speaker must possess sincerity, a good platform manners, and has the ability to express his thoughts. 4) Good speakers must possess sincerity, a good platform manner, and the ability to express thoughts. 5) The good speaker must possess sincerity, good platform manner, and ability to express his thought