大全-20-2，6，13

2.     Mud from a lake on an uninhabited wooded island in northern Lake Superior contains toxic chemicals, including toxaphene, a banned pesticide for cotton that previously was manufactured and used, not in nearby regions of Canada or the northern United States, but in the southern United States. No dumping has occurred on the island. The island lake is sufficiently elevated that water from Lake Superior does not reach it.

The statements above, if true, most strongly support which of the following hypotheses?

(A) The waters of the island lake are more severely polluted than those of Lake Superior.

(B) The toxaphene was carried to the island in the atmosphere by winds.

(C) Banning chemicals such as toxaphene does not aid the natural environment.

(D) Toxaphene has adverse effects on human beings but not on other organisms.（B）

(E) Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient of be measurable.

6.     otato cyst nematodes are a pest of potato crops. The nematodes can lie dormant for several years in their cysts, which are protective capsules, and do not emerge except in the presence of chemicals emitted by potato roots. A company that has identified the relevant chemicals is planning to market them to potato farmers to spread on their fields when no potatoes are planted; any nematodes that emerge will soon starve to death.

Which of the following, if true, best supports the claim that the company’s plan will be successful?

(A) Nematodes that have emerged from their cysts can be killed by ordinary pesticides.

(B) The only part of a potato plant that a nematode eats is the roots.

(C) Some bacteria commonly present in the roots of potatoes digest the chemicals that cause the nematodes to emerge from their cysts.

(D) Trials have shown that spreading even minute quantities of the chemicals on potato fields caused nine-tenths of the nematodes present to emerge from their cysts.（D）

(E) The chemicals that cause the nematodes to emerge from their cysts are not emitted all the time the potato plant is growing.

13.   Many state legislatures are considering proposals to the effect that certain policies should be determined not by the legislature itself but by public referenda in which every voter can take part. Critics of the proposals argue that the outcomes of public referenda would be biased, since wealthy special-interest groups are able to influence voters’ views by means of television advertisements.

Which of the following, if true, most strengthens the critics’ argument?

(A) Many state legislators regard public referenda as a way of avoiding voting on issues on which their constituents are divided.

(B) During elections for members of the legislature, the number of people who vote is unaffected by whether the candidates run television advertisements or not.

(C) Proponents of policies that are opposed by wealthy special-interest groups are often unable to afford advertising time on local television stations.

(D) Different special-interest groups often take opposing positions on questions of which policies the state should adopt.（C）

(E) Television stations are reluctant to become associated with any one political opinion, for fear of losing viewers who do not share that opinion.

终于贴完了， expecting

Q2why is B?