Which of the Following Is Not a Piece of Good

Which of the following is not a piece of good advice regarding business e-mails?

A) Do not sign off your e-mails with a closing like "Thank you"; it just wastes space.Simply send your contact information.
B) Do not place anything in an e-mail you would not want the world to see.
C) Do not use capital letters for your message.
D) Do not hit the send button until you check your e-mail.