Passage One
The study of genetics has given rise to a profitable new industry called biotechnology. As the name suggests, it blends biology and modem technology through such techniques as genetic engineering. Some of the new biotech as they are called, specialize in agriculture and are working enthusiastically to patent seeds that give a high yield, that resist disease, drought, and frost, and that reduce the need for hazardous chemicals. If such goals could be achieved, it would be most beneficial. But some have raised concerns about genetically engineered crops.
"In nature, genetic diversity is created within certain limits," says the book Genetic Engineering, Food, and Our Environment. "A rose can be crossed with a different kind of rose, but a rose will never cross with a potato. Genetic engineering, on the other hand, usually involves taking genes from one species and inserting them into another in an attempt to transfer a desired prope
A. within the limits of natural genetics
B. by violating laws of natural genetics
C. without the interference of humans
D. safer than those without the use of biotechnology
阅读下面短文,回答下面问题。 树是一部活档案,树干的年轮就是历史的记录。1901年,美国人道格拉斯发现居住地附近新近砍伐留下的树桩上,都有相同的图案纹理,譬如说,这些树木年轮的外面三圈都较宽,这表明近3年居住地附近环境与气候条件较好,树木生长较快。担相反的结论也可以由此得出。这个发现促使道格拉斯致力于树木年乾的深入研究。他用“同一地区,同时期年轮模式相同”的假设,以“接龙”的方式,来推算老树的初生年份。比如,有一棵被砍伐的百年古树,其砍伐年代不详,但是它的年轮中有一圈与当地一棵1864年砍下的大树的年轮最外圈相吻合。由于最外圈是被砍伐当年的年轮,因此这相吻合的一圈为1864年的年轮。由此向内按每进一圈是一年的方法推算,就可以算出这棵树大约哪一年栽种的。 一些科学家还根据年轮推算出发生过酸雨的年份。哥伦比亚大学的雅格比解释说,随着树木越长越老,年轮也变得越来越窄,而酸雨对树木恰恰起着相反的作用。年轮还可以记录下火山爆发与地震。火山爆发时,大量灰尘与气体进入同温层,遮住了阳光,这会使温度降到冰点以下,给树木留下一道叫做“霜轮”的特殊标记。东印度群岛坦波拉山爆发曾使1816年成了“没有夏天的一年”,这个标记甚至出现在南非的树木上。地震也可以给树木造成损害,使树在以后的一些年中形成较窄的年轮。由此看来,倘若说树木年轮“泄漏天机”,似乎并不为过。 (佚名《年轮》) |
黑盒测试和白盒测试分别是从()角度出发的测试,白盒测试重视()的度量。
白盒测试重视()的度量。我来回答: