听力原文：Have you ever encountered a system breakdown because of a computer crash？ It may

听力原文： Have you ever encountered a system breakdown because of a computer crash？ It may have started from a single Infectious file which runs through every computer in the world. And such a nasty computer virus is known to freeze the main operating system temporarily and hide within it to reproduce itself into a bigger infection, resulting in file deletion.

You should then subscribe to our anti-virus service, which provides 24-hour, worry-free protection through on and off line scanning. It has an automatic update function which can be done even during virus outbreaks. Our program will safely isolate and neutralize any infected files and restore lost files. Our online service also includes chat-based support from our certified technicians 24 hours a day. There are several system requirements on your computer however. Any interested customers must be using a computer with a 486 or higher processor and have at least 256 megabytes of RAM. Windows XP is preferred but not required. A one-year subscription costs only $49.99, so don't delay! We urge you to protect your computer as new and more powerful virus threats appear constantly.

7 What is being advertised？

A．A new computer.

B．A new chat site.

C．A computer store.

D．An anti-virus software program.