A project's payback period ends when ______ .

A:profit maximum is realized B:unit profit is realized C:monthly revenue exceeds monthly costs D:cumulative revenue equals cumulative costs

Text 3
Potential AIDS victims who refuse to be tested for the disease and then defend their right to remain ignorant about whether they carry the virus are entitled to that right. But ignorance cannot be used to rationalize irresponsibility. Nowhere in their argument is their concern about how such ignorance might endanger public health by exposing others to the virus.
When a disease selectively attacks the socially disadvantaged, such as homosexuals and drug abusers, it seems an injustice beyond rationalization. Such is the case with acquired immune deficiency syndrome.
Some crucial facts: AIDS is a communicable disease. The percentage of those infected with the AIDS virus who will eventually contract the disease is unknown, but that percentage rises with each new estimate. The disease so far has been 100 potential. The latency period between the time the virus is acquired and the disease develops is also unknown.
We now have tests for the presence of the virus that is as efficient and reliable as almost any diagnostic test in medicine. An individual who tests positive can be presumed with near-certainty to carry the virus, whether he has the disease or not.
To state that the test for AIDS is "ambiguous", as a clergyman recently in public, is a misstatement and an immoral act. The test correlates so consistently with the presence of the virus in bacteria cultures as to be considered 100 percent certain by experts.
Everyone who tests positive must understand that he is a potential person for the AIDS virus and has a moral duty and responsibility to prevent others from infection. We are not just dealing with the protection of the innocent but with an essential step lo contain the spread of an epidemic as horrible as any that has befallen modern man.
It may seem unfair to burden the tragic victims with concern for the welfare of others. But moral responsibility is not a luxury of the fortunate, and evil actions committed in despair cannot be condemned out of pity. It is morally wrong for a healthy individual who tests positive for AIDS to be involved with anyone except under the strict precautions now defined as safe sex.
It is morally wrong for someone in a high risk population who refuses to test himself to do other than to assume that he tests positive. It is morally wrong for those who, out of sympathy for the heartbreaking victims of this epidemic, as though well-wishing and platitudes about the ambiguities of the disease are necessary in order to comfort the victims while they contribute to enlarging the number of those victims. Moral responsibility is the burden of the sick as well as the healthy.

A:the growing period. B:the inactive period. C:the acute stage. D:the chronic stage.

Text 3 Potential AIDS victims who refuse to be tested for the disease and then defend their right to remain ignorant about whether they carry the virus are entitled to that right. But ignorance cannot be used to rationalize irresponsibility. Nowhere in their argument is their concern about how such ignorance might endanger public health by exposing others to the virus. When a disease selectively attacks the socially disadvantaged, such as homosexuals and drug abusers, it seems an injustice beyond rationalization. Such is the case with acquired immune deficiency syndrome. Some crucial facts: AIDS is a communicable disease. The percentage of those infected with the AIDS virus who will eventually contract the disease is unknown, but that percentage rises with each new estimate. The disease so far has been 100 potential. The latency period between the time the virus is acquired and the disease develops is also unknown. We now have tests for the presence of the virus that is as efficient and reliable as almost any diagnostic test in medicine. An individual who tests positive can be presumed with near-certainty to carry the virus, whether he has the disease or not. To state that the test for AIDS is "ambiguous", as a clergyman recently in public, is a misstatement and an immoral act. The test correlates so consistently with the presence of the virus in bacteria cultures as to be considered 100 percent certain by experts. Everyone who tests positive must understand that he is a potential person for the AIDS virus and has a moral duty and responsibility to prevent others from infection. We are not just dealing with the protection of the innocent but with an essential step lo contain the spread of an epidemic as horrible as any that has befallen modern man. It may seem unfair to burden the tragic victims with concern for the welfare of others. But moral responsibility is not a luxury of the fortunate, and evil actions committed in despair cannot be condemned out of pity. It is morally wrong for a healthy individual who tests positive for AIDS to be involved with anyone except under the strict precautions now defined as safe sex. It is morally wrong for someone in a high risk population who refuses to test himself to do other than to assume that he tests positive. It is morally wrong for those who, out of sympathy for the heartbreaking victims of this epidemic, as though well-wishing and platitudes about the ambiguities of the disease are necessary in order to comfort the victims while they contribute to enlarging the number of those victims. Moral responsibility is the burden of the sick as well as the healthy.

A:the growing period. B:the inactive period. C:the acute stage. D:the chronic stage.

Exercise Whether or not exercise adds to the length of life, it is common experience that a certain amount of regular exercise (51) health and contributes a feeling of well-being. Furthermore, exercise (52) involves play and recreation (娱乐), and relieves nervous tension and mental fatigue in so (53) , is not only pleasant but beneficial. How much and what kind of exercise one should (54) merits careful consideration. The growing child and the normal young man and young woman thrill (兴奋) with the exhilaration of strenuous sports. They fatigue to the (55) of exhaustion but recover promptly with a period of rest. But not so with those of middle age and beyond. For them moderation is (56) vital importance. Just how much exercise a person of a given age can safely take is a question hard to (57) . Individual variability is too great to permit generalization. A game of tennis may be perfectly safe for one person of forty but folly (愚蠢) for another. The safe (58) for exercise depends on the condition of the heart, the condition of the muscles, the (59) of exercise, and the regularity with which it is taken. Two general suggestions, however, will (60) as sound advice for anyone. The first is that the (61) of the heart and general health should be determined periodically by careful, thorough physical examinations. The other is that exercise should be kept (62) the point of physical exhaustion. What type of exercise one should (63) depends upon one’s physical condition. Young people can safely enjoy competitive sports, but most older persons do better to limit themselves to less strenuous (64) . Walking, swimming and skating are among the sports that one can enjoy and safely (65) in throughout life. Regularity is important if one is to get the most enjoyment and benefit out of exercise.

A:approach B:distance C:period D:limit

In a computer，which of the following is the longest period? （）

A:Beat period B:Machine period C:Instruction period D:CPU period

There are several periods in a computer, the longest period is

A:Instruction period B:Machine period C:Beat period D:CPU period

There are several periods in a computer, the longest period is ( ).

A:instruction period B:machine period C:beat period D:CPU period

There are several periods in a computer, the shortest period is( ).

A:instruction period B:machine period C:beat period D:CPU period

In a computer, which of the following is the longest period ？（）

A:Beat period B:Machine period C:Instruction period D:CPU period