Scientists are debating how to limit their newly-discovered power to change genetic structure (结构). Scientists already modify the genes (基因) 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 (物种) 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 (释放) into the wild.

   Sixteen biologists, ethicists (伦理学家) 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 (生物体) 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 (繁殖).

  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.

(1) What possible advantage does gene control in wild animals and plants have?
A. Changing the Zika virus permanently. B. Having the changed genes in their next generations. C. Getting rid of damaging species forever. D. Making all the species more productive and stronger.
(2) As for genetically changed wild animals and plants, what are scientists worried about?
A. Their genes may spread to later generations. B. They may be more productive than before. C. They may cause damage to their living habitat. D. They may become weaker or die out.
(3) Which of the following is true according to the passage?
A. Gene modification can benefit some farm animals and agricultural plants. B. Scientists are certain what exact results gene modification leads to. 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.
(4) The article is mainly intended to ______.
A. appeal against research on gene control B. inform us of power and danger of gene control C. show how to change genetic structure D. give the reason why gene modification is necessary