世界煤炭储量在世界能源总储量中占90%。按目前规模开采可持续200年左右。据19世纪

在年最高温度超过40℃，而且长期处于低湿度的干热地区，应选用型号后带（）字样的干热带型产品。

A.TA

B.TH

C.TT

D.TN

以下哪项不是X线产生应具备的条件()

A．电子云

B．高真空

C．电子的骤然加速

D．阳极靶

E．电子的高速运动

调研数据分析方法中以下哪一层不是（）

A.第一层数据图表化

B.第二层描述性统计

C.第三层显著性分析

D.第四层综合性汇总

患者，身目俱黄，但不如热重于湿型鲜明，多无发热，头重身困，口淡不渴，胸脘痞满，恶油腻，不欲食，腹胀便溏，舌苔厚腻，脉濡而数。诊为

A．湿热并重型黄疸
B．湿热蕴蒸，湿重于热型的黄疸
C．寒湿阻遏型黄疸
D．湿热蕴蒸，热重于湿型的黄疸
E．脾亏血虚型黄疸

The questions in this group are based on the content of a passage. After reading the passage, choose the best answer to each question. Answer all questions following the passage on the basis of what is stated or implied in the passage.

Although hard statistics are difficult to come by, there is substantial anecdotal evidence that use of performance-enhancing drugs, or doping, is rampant in professional sports. Of perhaps greater significance to society are the estimated 1.5 million amateur athletes who use steroids, either to improve their appearance or to emulate the performance of their favorite professional athletes. This chemical epidemic is a pernicious threat to both the nation’s health and our collective sense of "fair play."

Nonprescription anabolic steroids have been illegal in the United States since 1991, and most professional sports leagues have banned them since the 1980s. These bans are partly a matter of fairness--a talented athlete trained to the peak of her ability simply cannot compete with an equivalent athlete using steroids--but also based on issues of health. Anabolic androgenic steroids ("anabolic" means that they build tissues; "androgenic" means that they increase masculine traits) have been linked to liver damage, kidney tumors, high blood pressure, balding, and acne. They function by increasing the body’s level of testosterone, the primary male sex hormone. In men, this dramatic increase in testosterone can lead to the shrinking of testicles, infertility, and the development of breasts; in women, it can lead to the growth of facial hair and permanent damage to the reproductive system. Steroids have also been linked to a range of psychological problems, including depression and psychotic rage.

The punishments for getting caught using steroids are severe, and the serious health consequences are well documented. Despite this, millions of professional and amateur athletes continue to use performance-enhancing drugs. Why is this

One clear pattern is that many athletes will do whatever it takes to get an edge on the competition. Since the 1950s, Olympic athletes have played a cat-and-mouse game with Olympic Committee officials to get away with doping, because the drugs really do work. Athletes who dope are simply per and faster than their competitors who play fair. Professional athletes in football and baseball have found that steroids and human growth hormone can give them the edge to score that extra touch-down or home run, and in the modern sports market, those results can translate into millions of dollars in salary. For the millions of less talented athletes in gyms and playing fields across the country, drugs seem like the only way to approach the abilities of their heroes in professional sports.

The other clear pattern, unfortunately, is that it has been all too easy for abusers to get away with it. Steroid abuse is often regarded as a "victimless crime." One of the favored ways to trick the testers is to use "designer" steroids. There are thousands of permutations of testosterone, such as THG, that can be produced in a lab. Chemists have discovered that they can create new drugs that produce androgenic effects but do not set off the standard doping tests. Other methods have been to use the steroids but stop a few weeks before testing, to use other chemicals to mask the traces of steroids, or to switch in a "clean" sample of urine at the testing site. Other athletes use steroid precursors, such as androstene-dione, that have androgenic effects similar to those of steroids but are not illegal because they are not technically steroids. The sad fact is that unless the government and professional sports organizations are willing to get tough on the steroid problem, the use of performance-enhancing dugs in sports is not going to end.

Which of the following best expresses the role of the third paragraph in the overall structure of the passage ？（）

A. It redirects the theme of the passage from presenting a problem to explaining the reasons for the problem’s severity.

B. It introduces a new concept that defines the rest of the passage.

C. It provides an answer to a question posed in the first two paragraphs.

D. It refutes the central hypothesis of the second paragraph and poses a question that is answered in the following paragraphs.

E. It narrows the focus of the passage from the general themes of the first two paragraphs to the more specific themes of the last two paragraphs.