请认真阅读下面各题，从题中所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
21. John was late for the business meeting because his flight had been by a heavy storm.
A. kept B. stopped C. slowed D. delayed
22. We _________ him not to play dirty tricks, but he wouldn’t listen.
A. persuaded B. advised C. suggested D. admitted
