Which of the Following Is NOT True

Which of the following is NOT true?

A) You should not shut down your PC before you clean your keyboard.
B) A can of compressed air is effective for blowing off the dust and dislodging larger debris from a keyboard.
C) To clean a keyboard, you can use cotton swabs just slightly moistened with a mild cleaning fluid.
D) Dust and fingerprint smudges can easily accumulate on your computer screen and make it quite difficult to read.