单项选择题

When you go online, are you peppered with pop-up ads If you are annoyed by them and find yourself chasing them around with your mouse until you can zap them off the screen, here’s a new twist. The next generation of pop-ups may be implanted in your PC soft-ware. When you turn on your computer, a "silent" software program slips on also, tracking the Web sites you visit and collecting information about any purchases you make. Then, when you visit other Web sites, targeted ads pop up on your screen-the ones for goods and services that you might be interested in buying. Suppose you initially browse through a site for outdoor gear and buy a fleece jacket. Two days later, your screen might show pop-ups for adventure travel, airline tickets, out door clothing, and the like. You might not even be aware of it, but these pop-ups are the result of the embedded software that some people call spyware.
The largest creator of this software, Gator, recently teamed up with Yahoo to send such pop-ups to 43 million computer screens worldwide. In one year the agreement generated 28 mil lion in advertising fees that were split by the two companies, and industry experts expect that figure to increase. While Yahoo insists that it is providing a service to its customers by offering more advertising choices, many consumers are less than pleased by the software or the ads. Concerned about invasion of privacy, some who discover the programs on their PCs ask service technicians to remove it. Gator, whose advertising customers include Verizon and American Express, presents itself as a way for consumers to "find bargains. " Marketing head Scott Eagle says that Gator’s model of targeting ads to specific consumers is far more efficient than "spraying ads across everybody. " However, companies such as Hertz and The Washington Post Inc. filed law suits against Gator for infringement of copyright and trademark laws, claiming that its ads were getting a "free ride" on their sites.
Not surprisingly, surveys focusing on the Internet experience typically list pop-up ads as the most annoying online experience. So marketers at Atlanta-based EarthLink came up with an idea: offer subscribers software to block them. Although EarthLink, the No. 3 U. S. Internet service provider with about five million subscribers, is small change in an industry dominated by industry giant AOL, the company has based its recent market growth strategy on offering a solution to the estimated 4.8 billion ads that pop up on computer screens worldwide every month.
Why do marketers continue to rely on such a disliked form of online advertising The answer is cost. Pop-up ads are inexpensive to produce and cost nearly nothing to send. But they are so annoying to some computer users that dozens of special programs have been written to block them from appearing on the screen during Internet use.
What are "pop-up ads"

A. The pictures chasing the PC users around.
B. The pages the PC users can zap off.
C. The online bursting advertising.
D. The ads tracking the Web sites.