If athletes want better performances, they should train at high altitudes. At higher altit

If athletes want better performances, they should train at high altitudes. At higher altitudes, the body has more red blood cells per unit volume of blood than at sea level. The red blood cells transport oxygen, which will improve performance if available in greater amounts. The blood of an athlete who trains at high altitudes will transport more oxygen per unit volume of blood, improving the athletes performance. Which of the following, if true, would be most damaging to the argument above, provided that the athletes heart rate is the same at high and low altitudes?

A.Scientists have found that an athlete"s heart requires a period of time to adjust to working at high altitudes.

B.Scientists have found that the body" s total volume of blood declines by as much as 25 percent at high altitudes.

C.Middle-distance runners who train at high altitudes sometimes lose races to middle-distance runners who train at sea level.

D.The performances of athletes in competitions at all altitudes have improved markedly during the past twenty years.

E.At altitudes above 5,500 feet, middle-distance runners often better their sea-level running times by several seconds .


  • 悬赏:0 答案豆
  • 提问人:00****10
  • 发布时间:2019-01-14
As a practical matter, the copper available for industrial use should not be thought of as limited by the quantity of copper deposits, known or unknown. The transmutation of one chemical element into another is a modern reality, through the methods of nuclear physics. Therefore, the quantity of a natural resource such as copper cannot be calculated even in principle, because copper can be made from other metals. Which of the following, if true, is the strongest argument against the argument above?

A.Although it is possible that additional deposits of copper will be found, geological considerations strongly indicate that they will not amount to more than a fifty-year supply.

B.The production of copper from other metals in industrial quantities would be prohibitively expensive in energy and materials.

C.Synthetic materials have been discovered that can serve as practical substitutes for copper in most of its uses.

D.It will be impractical, in the foreseeable future, to mine any deposits of metal that may exist on the Moon or on other planets.

E.Methods for estimating the amount of copper available in currently known deposits have become very sophisticated and have proved quite accurate.

The excessive number of safety regulations that the federal government has placed on industry poses more serious hardships for big businesses than for small ones. Since large companies do everything on a more massive scale, they must alter more complex operations and spend much more money to meet governmental requirements. Which of the following, if true, would most weaken the argument above?

A.Small companies are less likely than large companies to have the capital reserves for improvements.

B.The operations of small companies frequently rely on the same technologies as the operations of large companies.

C.Safety regulation codes are uniform, established without reference to size of company.

D.Large companies typically have more of their profits invested in other businesses than do small companies.

E.Large companies are in general more likely than small companies to diversify their markets and products.

Since the Airline Deregulation Act of 1978, major airline companies in the United States have cut their employee ranks by more than 3,000 persons. Thus, although deregulated competition has afforded consumers dramatically lower fares, the economy of the United States has been harmed by deregulation of the airlines. The argument above would be most seriously weakened if it were true that

A.a poll of people in the United States expressed exceptionally strong support for airline deregulation.

B.fewer passengers now travel on commercial airlines than traveled on them in 1978, with the consequence that fewer employees are needed to operate the airlines than were needed in 1978.

C.airlines now fly a more restricted regular schedule of routes than they did in 1978, with the consequence that the industry is more highly concentrated and competitive than it was before 1978.

D.several major airlines now enjoy significantly higher profits and levels of employment than they did in the years preceding the Deregulation Act.

E.smaller carriers of passengers have thrived as a result of deregulation and now provide more new jobs than the major airlines have eliminated since 1978.

Some soil scientists have asserted that decaying matter on the forest floor is a far greater source of the acidity in mountain lakes than is the acid rain that falls on these lakes. Therefore, they contend, reducing acid rain will not significantly reduce the acidity levels of mountain lakes. Which of the following statements, if true, most seriously weakens the argument above?

A.It is natural for mountain lakes to have acidity levels higher than those of other lakes.

B.The harmful effects of increased acidity levels in lakes have been greatly underestimated.

C.Acid rain is found in urban and heavily industrialized regions of the country.

D.There is much disagreement among soil scientists about the causes of acid rain.

E.While plant life remains, acid rain significantly increases the amount of decaying organic matter in natural environments.



图形验证:看不清?点击更换 换一换
  • 49.8

    ¥75 每天只需0.6元
    3个月 推荐
  • 39.8

  • 99.8



  • 微信付款
  • 支付宝付款



恭 喜 您 获 得
扫 码 免 费 领 取
会 员 或 搜 题 次 数