Passage One
　　In the villages of the English countryside there are still people who remember the good old days when no one bothered to lock their doors. There simply wasn't any crime to worry about.
　　Amazingly, these happy times appear still to be with us in the world's biggest community. A new study by Dan Farmer, a gifted programmer, using an automated investigative program of his own called SATAN, shows that the owners of well over half of all World Wide Web sites have set up home without fitting locks to their doors.
　　SATAN can try out a variety of well-known hacking (黑客的) tricks on an Internet site with­out actually breaking in. Farmer has made the program publicly available, amid much criticism. A person with evil intent could use it to hunt down sites that are easy to burgle (闯入……行窃).
　　But Farmer is very concerned about the need to alert the public to poor security and, so far, events have proved him right. SATAN has done more to alert people to the risks than cause new disorder.
　　So is the Net becoming more secure? Far from it. In the early days, when you visited a Web site your browser simply looked at the content. Now the Web is full of tiny programs that automatically download when you look at a Web page, and run on your own machine. These programs could, if their authors wished, do all kinds of nasty things to your computer.
　　At the same time, the Net is increasingly populated with spiders, worms, agents and other types of automated beasts designed to penetrate the sites and seek out and classify information. All these make wonderful tools for antisocial people who want to invade weak sites and cause damage.
　　But let's look on the bright side. Given the lack of locks, the Internet is surely the world's biggest (almost) crime-free society. Maybe that is because hackers are fundamentally honest. Or that there currently isn't much to steal. Or because vandalism ( 恶意破坏) isn't much fun unless you have a peculiar dislike for someone.
　　Whatever the reason, let's enjoy it while we can. But expect it all to change, and security to become the number one issue, when the most influential inhabitants of the Net are selling services they want to be paid for.

　　21. By saying “... owners of well over half of all World Wide Web sites have set up home without fitting locks to their doors" (Lines 3-4, Para. 2), the author means that _____.
　　A) those happy times appear still to be with us
　　B) there simply wasn't any crime to worry about
　　C) many sites are not well-protected
　　D) hackers try out tricks on an Internet site without actually breaking in

　　22. SATAN, a program designed by Dan Fanner can be used ____________.
　　A) to investigate the security of Internet sites
　　B) to improve the security of the Internet system
　　C) to prevent hackers from breaking into websites
　　D) to download useful programs and information

　　23. Fanner's program has been criticized by the public because.
　　A) it causes damage to Net browsers
　　B) it can break into Internet sites
　　C) it can be used to cause disorder on all sites
　　D) it can be used by people with evil intent

　　24. The author's attitude toward SATAN is _____.
　　A) enthusiastic C) positive
　　B) critical D) indifferent

　　25. The author suggests in the last paragraph that.
　　A) we should make full use of the Internet before security measures are strengthened
　　B) we should alert the most influential businessmen to the importance of security
　　C) influential businessmen should give priority to the improvement of Net security
　　D) net inhabitants should not let security measures affect their joy of surfing the Internet