Which of the following genes are structural genes? (). A: The promoter B: The enhancer C: The silencing D: The guide protein synthesis

短篇新闻听力训练7-2Question 3 and 4 will be based on the following news. A: Questioning the U.N. Committee Against Torture. B: Torturing terror suspects. C: Prohibiting military operations in Quantanamo Bay. D: Silencing the critics of the U.S.

下列关于基因沉默或缺失验证基因功能的描述正确的是 A: 条件性基因敲除只能控制表达时间 B: 基因敲除可作为研究功能缺失的首选方法 C: 基因沉默（gene silencing）是指由外源基因导入引起的生物体内的特定基因不表达或表达受抑制的现象 D: 反义寡核苷酸也可以引发的基因沉默是在转录后发生 E: RNAi所使用的小RNA是内源单链的

Modern technology may not haveimproved the world all that much but it certainly has made life noisier. Unruffledmotorcycles, blaring car alarms, and roving boom boxes come first, second, andthird on my list of most obnoxious noise offenders, but everyone could come upwith his own version of aural hell – if he could just find a quiet spot toponder the matter. Yet what technology has done, othertechnology is now starting to undo, using computer power, to zap thoseear-splitting noises into silence. Previously silence-seekers had littlerecourse except to stay inside, close the windows, and plug their ears.Remedies like these are quaintly termed “passive” systems, because they placephysical barriers against the unwanted sound. Now computer technology isproducing a far more effective “active” system, which doesn’t just contain,deflect, or mask the noise, but annihilates it electronically. The system works by countering theoffending noise with “anti-noise”, a somewhat sinister-sounding term that callsto mind antimatter, black holes, and other Popular Science mindbenders but thatactually refers to something quite simple. Just as a wave on a pond isflattened when it merges with a trough that is its exact opposite (or mirrorimage), so can a sound wave be negated by meeting its opposite. This general theory of soundcancellation has been around since the 1930s. In the fifties and sixties itmade for a kind of magic trick among laboratory acousticians playing aroundwith the first clunky mainframe computers. The advent of low-cost high-powermicroprocessors has made active noise-cancellation systems a commercialpossibility, and a handful of small electronics firms in the United States and abroad are bringing the first ones onto the silence market. Silence buffs might be hoping that the noise-canceling apparatus will takethe shape of the 44 Magnum wielded by Dirty Harry, but in fact active soundcontrol is not quite that active. The system might more properly be describedas reactive, in that it responds to sound waves already headed toward humanears. In the configuration that is usual for such systems microphones detectthe noise signal and send it to the system’s microprocessor, which almostinstantly models it and creates its inverse for loudspeakers to fire at theoriginal. Because the two sounds occupy the same range of frequencies andtones, the inverse sounds exactly like the noise it is to eliminate, theanti-noise canceling Beethoven’s Fifth Symphony is heard as Beethoven’s Fifth.The only difference is that every positive pressure produced on the air by theorchestra is matched by a negative pressure produced by the computer, and everynegative pressure is matched by a positive, thereby silencing the sound. The systemis most effective as a kind of muffler, in which microphones, micro-processor,and loudspeaker are all in a unit encasing the device that produces the sound,stifling it at its source. But it can work as a headset, too, negating thesound at the last moment before it disturbs one’s peace of mind. 1. The writer holds that( ). A. modern technology has disturbed thequiet life of the people B. moderntechnology has made people indifferent to noise pollution C. moderntechnology has made the present world quieter than before D.modern technology has failed to solve the problem of noise pollution 2. According to the passage,an active noise-cancellation system ( ). A. contains noise rather than negates it B. eliminates noise rather than muffles it C. deflects noise rather than baffles it D. holds noise back rather than stifles it 3. In paragraph 5 the word “buffs”means ( ). A. settlers B.enthusiasts C. buyers D. manufacturers 4. Which of the followingstatements is NOT true according to the passage? ( ) A.In the past, people sometimes plugged their ears to fight against the offendingnoise. B. An active noise-cancellation systemfollows the principle of a wave being flattened by meeting its exact opposite. C. The first active noise-cancellationsystem was made in the 1930s. D. Active noise-cancellation systems are nowavailable on the market. 5. Activenoise-cancellation systems require ( ). A. microphones B.microprocessors C.loudspeakers D. all of theabove