B

Scientists are debating how to limit their newly-discovered power to change genetic structure (结构). Scientists already modify the genes of farm animals and agricultural plants to make them more productive or stronger. But now they can also change genes in wild animals and plants. These genes would continue into later generations. For example, it may be possible for scientists to remove from existence the kind of mosquitoes, small flying insects, that carry the Zika virus. They might also be able to permanently remove species of plants and animals that are damaging to other species.

In a report published last week, the U. S. National Academies of Sciences, Engineering and Medicine (NAS) said it supports continued research on this kind of gene control. But it warned that it is not possible to know what will happen when these changed plants and animals are released into the wild.

Sixteen biologists, ethicists and policymakers are on an NAS committee that is examining the issue. They say that there is value to the new technology. But, they say, there is not enough evidence to support the release of modified organisms from the laboratory into nature.

Many people would support stopping mosquitoes and rats from carrying diseases. But scientists say we must understand the possible scientific, ethical, legal and social results of such action before we decide whether to take it. Gene modification is spread through reproduction.

Changed genes will continue to spread as long as an animal or plant continues to reproduce. They cannot be limited to a farm or kept within a country's borders. Scientists are wondering what may happen if a modified organism mates with another species. They are not yet sure how the modified genes would affect the other species. It is possible that those genes could harm those creatures or even lead to their disappearance from our planet.

58. What possible advantage does gene control in wild animals and plants have?

A. Changing the Zika virus permanently. B. Getting rid of damaging species forever.

C. Having the changed genes in their next generations.

D. Making all the species more productive and stronger.

59. Which of the following is true according to the passage?

A. Scientists are certain what exact results gene modification leads to.

B. Gene modification can benefit some farm animals and agricultural plants.

C. Scientists won't modify any genes before they make the final decision.

D. Gene modification will be encouraged in more creatures in the near future.

60. The article is mainly intended to ______.

A. appeal against research on gene control B. show how to change genetic structure

C. inform us of power and danger of gene control

D. give the reason why gene modification is necessary

C

Elderly women who eat foods higher in potassium(钾)are less likely to have strokes and die than women who eat less potassium-rich foods, according to new research in the American Heart Association. “Previous studies have shown that potassium consumption may lower blood pressure. But whether potassium intake could prevent stroke or death wasn抰 clear,?said Smoller, professor of the department of population health at Albert Einstein College of Medicine, Bronx, NY.

Researchers studied 90,137 women, aged from 5ay0 to 79 for an average 11 years. They looked at how much potassium the women consumed, as well as if they had strokes, including ischemic strokes (缺血性中风), or died during the study period. Women in the study were stroke-free at the start and their average dietary potassium intake was 2,611 mg/day. Results of this study are based on potassium from food, not supplements.

The researchers found: Women who ate the most potassium were 12 percent less likely to suffer stroke in general and 16 percent less likely to suffer an ischemic stroke than women who ate the least. Women who ate the most potassium were 10 percent less likely to die than those who ate the least. Among women who did not have high blood pressure, those who ate the most potassium had a 27 percent lower ischemic stroke risk and 21 percent reduced risk for all stroke types, compared to women who ate the least potassium in their daily diets. Among women with high blood pressure, those who ate the most potassium had a lower risk of death, but potassium intake did not lower their stroke risk.

?Our findings suggest that women need to eat more potassium-rich foods. You won’t find high potassium in junk food. Some foods rich in potassium include white and sweet potatoes, bananas and white beans.”

The U.S. Department of Agriculture recommends that women eat at least 4,700 mg of potassium daily. “Only 2.8 percent of women in our study met or went beyond this level. The World Health Organization’s daily potassium recommendation for women is lower, at 3,510 mg or more. Still, only 16.6 percent of women we studied met or went beyond that,” said Smoller.

While increasing potassium intake is probably a good idea for most elderly women, there are some people who have too much potassium in their blood, which can be dangerous to the heart. “People should check with their doctor about how much potassium they should eat,” she said.

The study was observational and included only elderly women. Researchers also did not take sodium (钠) intake into consideration, so the potential importance of a balance between sodium and potassium is not among the findings. Researchers said more studies are needed to determine whether potassium has the same effects on men and younger people.

61. The benefits of potassium intake to elderly women do not include ______.

A. preventing strokes B. reducing heart attacks

C. cutting down death risks D. lowering blood pressure

62. Which of the following figure meets the daily potassium intake recommendation of the World Health Organization?

A. 4,000 mg B. 3,500 mg C. 3,000 mg D. 2,500 mg

63. What conclusion can be drawn from the research findings?

A. Increasing potassium is definitely a good idea for all elderly women.

B. Elderly women with high blood pressure benefit more from potassium.

C. Potassium intake is more beneficial to those without high blood pressure.

D. There was not any association between potassium intake and ischemic strokes.

64. The author’s purpose for writing this passage is to ______.

A. present a report on a new research B. show the importance of a good life style

C. give information about a chemical element D. encourage elderly women to take potassium