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  3. If you have ever wondered how an elephant smells, scientists have the answer. Researchers have discovered that African Elephants

If you have ever wondered how an elephant smells, scientists have the answer. Researchers have discovered that African Elephants

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问题     If you have ever wondered how an elephant smells, scientists have the answer. Researchers have discovered that African Elephants have the largest number of genes【C1】________smell of any mammal. Given the size of their trunks, and how important it is【C2】________their survival, it is probably unsurprising that an elephant’s nose is not only the longest in the animal kingdom, but also the most effective.
    In【C3】________, humans and other primates have a poor sense of smell. "The functions of these genes are not well known,【C4】________they are likely important for the living environment of African elephants," said author Dr Yoshihito Niimura of the University of Tokyo. "【C5】________, an elephant’s nose is not only long but also superior. " The sense of smell is【C6】________to all mammals, and they use it for【C7】________food, finding mates and locating their offspring.
    In a study published in Genome Research, scientists【C8】________the 13 mammal species and found that African Elephants have twice the number of smell genes【C9】________dogs and five times more than humans. They have around 2,000 genes alone that are associated with scent. Humans in comparison have just under 400 and some other primates even【C10】________. The study found that 20,000 genes are【C11】________for the sense of smeD in mammals, of which around half are functional, but the collections【C12】________for each species. Horses have around 1,000 smell genes, rabbits around 750 and rats about 1,200.
    "The large repertoire of elephant (smell) genes might be attributed to elephants’ heavy【C13】________on scent in various contexts, including social【C14】________and reproduction," added Dr Niimura. African and Asian elephants possess a【C15】________scent organ behind each eye, and male elephants can produce a special substance during annual mating, which is characterized【C16】________increased aggressiveness. And【C17】________studies have revealed that, African elephants can reportedly【C18】________between two Kenyan ethnic groups—the Maasai, whose young men【C19】________manhood by spearing elephants, and the Kamba, who are agricultural people that【C20】________little threat to elephants through smell.
【C18】
选项 A、utter
B、compare
C、notice
D、distinguish
答案D
解析 本文介绍的是大象的嗔觉，由上文可知其嗅觉非常灵敏，句末的through smell表明大象可以依靠气味辨别具有威胁性的部族。故选D项distinguish“区分，辨别”，表明大象可以通过气味分辨出两个不同的肯尼亚部族。A项utter“说”。指人的发音、说话。B项compare“比较”，强调对比的动作而不强调结果。C项notice“注意到”，常指看到什么东西，而不是对两个事物进行对比。
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