A
[2019·烟台高考诊断性测试]
Dogs and humans have been living sidebyside for about 15 000 years, but there are tons of facts about dogs that perhaps we have never heard of.
Night vision
Dogs have good night vision. Their large pupils let more light in and the rods(视杆细胞) work better in poor light. But the biggest factor is the tapetum(反光组织), which reflects light at the back of the eye. Besides, dogs' whiskers(胡须) also help them “see” in the dark because they pick up on very small changes in air, providing dogs with information about the size, shape, and speed of things nearby.
Secret tail code
Dogs can use their tails to communicate. They wag their tails to the right when they are relaxed or happy, and to the left when nervous or threatened. When they're aggressive, the tails will stick straight up in the air. A broad wag is friendly while a slow wag is neutral, neither excited nor anxious.
Dreams
We often see a dog's body making sudden movements in its sleep. Dogs have the same brain wave patterns as humans' while they are asleep, so they dream just like we do.
Super nose
Dogs can find their way home despite long distances. Their noses are a vital part of their incredible sense of direction. The part of a dog's brain that controls smell is 40 times larger than humans'. They're able to follow smells for miles. Furthermore, dogs have an amazing ability to recognize the smells given off by the abnormal cells in human bodies, including cancer. This is something scientists are eager to explore further. And interestingly, a dog's “fingerprint” is on its nose. The patterns on dogs' noses are so distinct that they can actually be used to identify the animals.
A sixth sense
Dogs act strangely before something bad, like a storm or earthquake, happens, for they are sensitive to low frequencies that humans can't sense. So don't let their strange behavior go unnoticed next time. It could save your life.
【文章大意】 本文是一篇说明文。文章主要介绍了关于狗的一些信息。
1．Which of the following indirectly helps dogs see well in the dark?
A．Their rods. B．Their tapetum.
C．Their whiskers. D．Their pupils.
答案与解析：C 考查细节理解。由第二段第四句Besides, dogs' whiskers(胡须) also help them “see” in the dark because they pick up on very small changes in air, providing dogs with information about the size, shape, and speed of things nearby.可知，狗的胡须能间接帮助它们在黑暗中看清东西，故正确答案为C。
2．If a dog holds up the tail, it indicates ________.
A．happiness B．attack
C．friendliness D．relaxation
答案与解析：B 考查细节理解。由第三段第三句“When they're aggressive, the tails will stick straight up in the air.”可知，当狗的尾巴笔直竖起时，它们有攻击性，故正确答案为B。
3．What hasn't been discovered about a dog?
A．Why it can sense natural disasters.
B．Why it has an acute sense of smell.
C．What emotions it shows with its tail.
D．How it can smell humans' illnesses.
答案与解析：D 考查细节理解。该题问的是有关狗的信息还有什么没有被发现。根据最后一段第一句可知，狗能感受到自然灾害是因为它们能感知到人类无法感知的低频率；根据第五段第三句可知，狗有敏锐的嗅觉是因为狗的大脑里控制嗅觉的部分比人类的要大40倍；根据第三段内容可知，狗的尾巴可以表达它的情绪；根据第五段倒数第三、四句可知，狗如何能嗅到人类的疾病还需要进一步的探索，故正确答案为D。
