单选题 In the second half of each year, many powerful storms are born in the tropical Atlantic and Caribbean seas. Of these, only about half a dozen generate the strong, circling winds of 75 miles per hour or more that give them hurricane status, and several usually make their way to the coast. There they cause millions of dollars of damage, and bring death to large numbers of people.
The great storms that hit the coast start as innocent circling disturbances hundreds—even thousands—of miles out to sea. As they travel aimlessly over water warmed by the summer sun, they are carried westward by the trade winds. When conditions are just right, warm, moist air flows in at the bottom of such a disturbance, moves upward through it and comes out at the top. In the process, the moisture in this warm air produces rain, and with it the heat is converted to energy in the form of strong winds. As the heat increases, the young hurricane begins to swirl in a counter-clockwise motion.
The average life of a hurricane is only about nine days, but it contains almost more power than we can imagine. The energy in the heat released by hurricane's rainfall in a single day would satisfy the entire electrical needs of the United States for more than six months. Water, not wind, is the main source of death and destruction in a hurricane. A typical hurricane brings 6-to 12-inch downpours resulting in sudden floods.

单选题 When is an ordinary tropical storm called a hurricane?
A. When it begins in the Atlantic and Caribbean seas.
B. When it hits the coastline.
C. When it is more than 75 miles wide.
D. When its winds reach 75 miles per hour.
【正确答案】 D
【答案解析】[解析] 根据文章开头第二句，在这许多强暴风中，只有风速达到或超过每小时75英里的旋风才称为飓风(hurricane)，所以D是正确答案。
单选题 What is the worst thing about hurricanes?
A. The destructive effects of hurricanes.
B. The heat they release.
C. That they last about nine days on average.
D. Their strong winds.
【正确答案】 A
【答案解析】[解析] 根据本文介绍，飓风破坏不光来自风力，还来自其携带的大量降水。选项B不是直接破坏力，C与题目无关，D以偏概全，只有A正确。
单选题 The counter-clockwise swirling of the hurricane is brought about by ______.
A. the low-pressure area in the center of the storm
B. the force of waves of water
C. the trade winds
D. the increasing heat
【正确答案】 D
【答案解析】[解析] 根据第二段最后一句，D是正确答案。
单选题 The word "downpour" means ______.
A. heavy rainfall
B. dangerous waves
C. the progress of water moving to the hurricane center
D. the energy produced by the hurricane
【正确答案】 A
【答案解析】[解析] 根据文章最后一句，一次典型的飓风带来6到12英寸downpours，造成突然的洪水暴发，从中可看出，downpours是指特大降雨，所以A是正确答案。
单选题 How long is the average life of a hurricane?
A. 19 days. B. 22 days. C. 9 days. D. 10 days.
【正确答案】 C
【答案解析】[解析] 根据第三段第一句，C是正确答案。