题目

细胞要经历产生、生长、成熟、增殖、衰老直至死亡的生命历程。下列相关叙述正确的是（ ）A.植物筛管细胞的形成是凋亡的结果B.衰老细胞中的酶的活性都显著降低，呼吸速率减慢C.衰老细胞的细胞核体积增大D.大肠杆菌分裂过程没有出现纺锤丝和染色体，也属于有丝分裂 答案：【答案】C【解析】1、细胞凋亡是由基因决定的细胞编程序死亡的过程。细胞凋亡是生物体正常的生命历程，对生物体是有利的，而且细胞凋亡贯穿于整个生命历程。2、衰老细胞的特征：细胞内水分减少，细胞萎缩，体积变小，但细胞核体积增大，染色质固缩，染色加深；细胞膜通透性功能改变，物质When someone is happy, can you smell it? You can usually tell when someone is happy based on seeing them smile, hearing them laugh or perhaps from receiving a big hug. But can you also smell their happiness? Surprising new research suggests that happiness does indeed have a scent, and that the experience of happiness can be transmitted through smell, reports Phys.org. For the study, 12 young men were shown videos meant to bring about a variety of emotions while researchers gathered sweat samples from them. All of the men were healthy and none of them were drug users or smokers, and all were asked to abstain from drinking or eating smelly foods during the study period. Those sweat samples were then given to 36 equally healthy young women to smell, while researchers monitored their reactions. Only women were selected to smell the samples, apparently because previous research has shown that women have a better sense of smell than men and are also more sensitive to emotional signaling—though it's unclear why only men were chosen to produce the scents. Researchers found that the behavior of the women after smelling the scents—particularly their facial expressions—indicated a relationship between the emotional states of the men who produced the sweat and the women who sniffed them. “Human sweat produced when a person is happy brings about a state similar to happiness in somebody who breathes this smell,” said study co-author Gun Semin, a professor at Koc University in Turkey. This is a fascinating finding because it not only means that happiness does have a scent, but that the scent is capable of transmitting the emotion to others. The study also found that other emotions, such as fear, seem to carry a scent too. This ensures previous research suggesting that some negative emotions have a smell, but it is the first time this has proved to be true of positive feelings. Researchers have yet to isolate(分离) exactly what the chemical compound for the happiness smell is, but you might imagine what the potential applications for such a finding could be. Happiness perfumes, for instance, could be invented. Scent therapies（香味疗法）could also be developed to help people through depression or anxiety. Perhaps the most surprising result of the study, however, is our broadened understanding of how emotions get communicated, and also how our own emotions are potentially managed through our social context and the emotional states of those around us. 1.What is the main finding of the new research?A. Pleasant feelings can be smelt out.B. Negative emotions have a smell.C. Men produce more sweats. D. Women have a better sense of smell.2.The underlined part “abstain from” in Paragraph 3 probably means _________.A. continue B. practice C. avoid D. try3.What is the application value of the new research? A. Perfumes could help people understand each other.B. Some smells could be created to improve our appearance.C. Perfumes could be produced to cure physical diseases.D. Some smells could be developed to better our mood.4. We can learn from the last paragraph that .A. happiness comes from a scent of sweatB. social surroundings can influence our emotions C. people need more emotional communicationD. positive energy can deepen understanding