单选题Questions 18 to 20 are based on the following passage. At the end of the passage, you will be given 15 seconds to answer the questions. Now, listen to the passage.
单选题
In which of the following places have snakes never been found?
【正确答案】
B
【答案解析】[听力原文] 18-20 Snakes may be found just about everywhere except the North Pole region and some islands in the South Pacific Ocean. Some snakes live in warm dry deserts; others live in green forests, fields and woodlands. Some never go far from water and are fine swimmers; some live all their lives in the sea. Most snakes can swim. Snakes are cold-blooded and depend on warm air for comfort and existence. The largest numbers of snakes are found in the hottest parts of the earth, even though many snakes stay away from the direct rays of the sun when possible. If extra hot weather comes along, snakes find the coolest place possible and stay there. In places where it freezes, snakes often hide themselves far under the ground or in caves and stay until spring. Snakes are smart enough to stay alive. They are smart enough to find food and kill their enemies. But, compared with other animals, they are believed to be below average in intelligence. 细节题，问世界上哪个地区还从未发现过蛇。从Snakes may be found just about everywhere except the North Pole region看出，北极地区从未发现过蛇，故答案是B。
单选题
Why do we find the largest number of snakes in hot regions?
【正确答案】
A
【答案解析】推断题，问蛇为何常在炎热地方出没。从they depend on warm air for comfort and existence可以看出，蛇类喜欢温暖环境，故答案是A。
单选题
How smart are snakes compared with other animals?
【正确答案】
B
【答案解析】推断题，问蛇类与别的动物相比之下的智商。从compared with other animals, they are believed to be below average in intelligence可以看出，蛇类显得不是那么聪明，故答案是B。