In the second half of each year, many powerful storms are born in the tropical Atlantic and Caribbean seas. Of these, only about a 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 (气旋) 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 (潮湿的) 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 that is switched to energy in the form of strong winds. As the heat increases, the young hurricane begins to turn around in a counter-clockwise motion (反时针方向).
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 (释放) by a hurricane’s rainfall in a single day would satisfy the entire electrical needs of the United States for more than six months.
Water, rather than wind, is the main source of death and destroying in a hurricane. A typical hurricane brings 6-to-12-inch downpours resulting in sudden floods. Worst of all is the powerful movement of the sea — the mountains of water moving toward the low-pressure hurricane center. The water level rises as much as 15 feet above normal as it moves toward shore.
An ordinary tropical storm is called a hurricane when ______.

A．it occurs in the Caribbean seas

B．its winds reach 75 miles per hour

C．it makes its way to the coastline

D．its winds begin to circle on the sea

What is the worst thing about hurricane?

A．The rough water.	B．The violent winds.
C．The heat it gives out.	D．The length of its life.

What does the third paragraph mainly talk about?

A．The hurricane is extraordinarily powerful.

B．The hurricane is used to generate electricity.

C．The hurricane can otherwise offer an unusual sight.

D．The hurricane can give people an unforgettable experience.

The counter-clockwise movement of the hurricane is caused by ______.

A．the low-pressure area in the center of the storm

B．the force of waves of water

C．the increasing heat

D．the trade winds