Suppose P and Q are logical expressions. The expression P || Q is true if both P and Q are true.

Which of the following is not true about viruses and worms?

A) Viruses are commonly spread through e-mail attachments, but they can also infect your computer when you download files or programs from the Internet. B) Once your computer is infected with a virus, the virus can attach itself to a program or file to spread to other users. C) Worms cannot carry viruses. D) Computer viruses are malicious programs installed on your computer without your knowledge and are programmed to destroy or damage data on your computer.

When describing a queuing system, we use the term ____________________ to refer to the time it takes to serve a customer.

Fill in the blank(s) with the appropriate word(s).