转基因作物同普通植物的区别只是多了能使它产生额外特性的基因。早在1983年，生物学家就已经知道怎样通过生物技术将外来基因移植到某种植物的脱氧核糖核酸中去，以便使它产生靠杂交方式根本无法获得的某种新特性：抗除莠剂的特性、抗植物病毒的特性、抗某种害虫的特性等。用以移植的基因可来自任何生命体：细菌、病毒、昆虫等。 下列对“转基因作物”这一概念的理解，正确的一项是( )。
A．因环境影响脱氧核糖核酸的变化而产生额外特性的作物
B．能够产生抗除莠剂、抗植物病毒等额外基因的作物
C．一种利用移植其他生命体基因而形成的新的杂交作物
D．移植了其他生命体基因从而产生额外特性的作物
参考答案：D
解析： A项错误，转基因作物与环境没有关系，是人工所为；B项错误，转基因作物是人工形成的，其基因不能自发产生；C项错误，转基因作物和杂交作物没有关系。故正确选项为D。
根据短文内容，从下框的A～F选项中选出能概括每一段主题的最佳选项，并在答题卡上将该选项涂黑。选项中有一项为多余项。
小题1: When it comes to understanding new information, the human brain needs a little time. First, we hear the words; then, we compare the new information to what we already know. If the two are different, we need to pause and think. But a breathless speaker never stops to let us think about what he or she is saying and risks confusing us. Slow it down. And breathe. 小题2: Sometimes we all start a sentence one way and then switch directions, which is very difficult to follow. When you confuse your listeners with opposing information, you leave the audience wondering what part of the information is right and what part they should remember. Instead of relying and keeping correcting yourself, work to get the facts clear and straight. 小题3: Jumping from point to point as it comes to your mind puts the onus (责任）on your listeners to make up for your lack of organisation. And it’s confusing for them to listen, reorganise, and figure out what you’re saying all at once. But going smoothly from one point to the next helps them understand information more easily. You can arrange things from beginning to end, small to large, top to bottom or by some other order. Just be sure to organise. 小题4: Repeated use of um, ah, like, you know and some other useless noises can drive an audience crazy. It makes the speaker sound uncertain and unprepared, and it can leave listeners so annoyed that they can’t pay attention. Recently I attended a speech that was marked by so many ums that audience members were rolling their eyes. Was anybody grasping the intended message? Um, probably not. 小题5: Many speakers finish up their speeches with question-and-answer (Q & A) sessions, but some let the Q & A go on without a clear end. The audience is often left confused about whether the meeting is over and when they can get up and leave. Do your listeners a favour by setting a time limit on questions, and close your speech with a specific signal—even if it’s something simple like, “If you have any more questions, you know where to reach me.” Or even more to the point, conclude your speech with “Thanks for your time. ” |