According to the author, which of the following statements is true

A．It is all right to set one's ringer to play Beethoven's Fifth, but not any other annoying melody.
B．Although people have realized the importance of switching off their cell phones during public performances, they keep forgetting to do it.
C．There are many people now who wear both their cell phones and pagers on the belt which makes them look like the Batman.
D．If you are afraid of not being heard clearly enough on the cell phone, raise your voice and that helps.