What is the MOST important thing you should do before transmitting on a marine radio? （）

A.Ask for permission

B.Record the time in your radio log

C.Press the push to talk button three times

D.Monitor the channel to insure that it is clear

相传，曹雪芹的祖父曹寅写的《题楝亭夜话图》是为了纪念谁而写的？