As with most things in life, being self-employed is not without problems. First, being one's own boss places the responsibility for success directly on that individual's shoulders. Abilities and intelligence will be put to the test. Everyone has some weaknesses and is less capable in some things than in others. These weaknesses will affect how successful a self-employed person is. Second, though the self-employed can earn considerable profits with a successful business, losses can force them out of business and, in some instances, place them in debt. A third disadvantage concerns income security. Self-employed people have no guaranteed wage. Their earnings can vary greatly from year to year, depending on business conditions. Salaried people, on the other hand, can generally count on continued earnings from year to year. In addition, salaried people often enjoy fringe benefits that mean greater peace of mind. Fringe benefits are all of the benefits provided for employees in addition to wages and salaries. One of these benefits may be insurance paid for by the employer that continues the employee's salary in the event of sickness or accident. Many self-employed people do not have such protection, unless they put money aside themselves.

21. A self-employed person is one _____________.
[A] who can make a big profit
[B] who is his or her own boss
[C] whose business has a better chance to success
[D] who employs no others but his or her relatives

22. One of the advantages self-employment offers is that self-employed people ________.
[A] may decide when and how long they work
[B] have outstanding abilities and intelligence
[C] may get more business support from the government
[D] are easy to earn money and ready to become wealthy

23. One problem of self-employment is that ___________.
[A] there is no guarantee of income security
[B] it is comparatively week in management
[C] an employer's earnings have nothing to do with business conditions
[D] salaries may vary greatly from person to person

24. We may guess from the context that fringe benefits _____________.
[A] are all the money provided for employees
[B] are benefits an employee receives apart from wages and salaries
[C] consist of those that are paid by insurance companies
[D] result from business activities the employer has organized

25. The author's attitude towards self-employment is ____________.
[A] positive
[B] negative
[C] indifferent
[D] objective

Passage Two
Questions 26 to 30 are based on the following passage.

Every living thing has what scientists call a biological clock that controls behavior. It tells plants when to form flowers and insects when to leave protective cocoon(茧)and fly away. And it tells animals and human beings when to awaken, sleep, and seek food. It controls our body temperatures, the release of some hormones(激素)and even dreams.

Events outside the plant and animal affect its actions. Scientists recently found that a tiny animal called Siberian hamster changes the color of its fur because of the number of hours of daylight. In shorter days of winter its fur becomes white. The fur becomes gray-brown in longer hours of daylight in summer.