Tuvalu, north of Fiji, is a tiny country in the Pacific Ocean.
Storms and huge waves are a constant threat and none of Tuvalu's nine little islands is more than five metres above sea level. Salt water is already entering the country's drinking water supply, as well as damaging plants that produce fruit and vegetable. It fears it will be swallowed up by the sea. Without urgent help, the country's days are numbered.
But Tuvalu is not the first place to face sinking into the sea. Venice, a historic city in Italy best known for its canals, has sunk about 24cm over the past 100 years. Experts say that it will have sunk another 20-50cm by 2050.A century ago, St. Mark's Square, the lowest point in the city, flooded about nine time a year. Nowdays it happens more than 100 times.
While Venice is slowly sinking into the mud on which it stands, Tuvalu's rising sea level is caused by global warming.
The average global temperature has increased by almost 0.5 centigrade degree over the past century; scientists expect it to rise by an extra 1-3 degrees over the next 100 years.
Warmer weather makes glaciers（冰川） melt, adding more water to the ocean. The warmer temperatures also make water expand, so it take up more space, causing the sea level to rise. The sea level has risen about 10-25cm in the last 100 years.
People have been increasing the greenhouse gases in the atmosphere, such as CO2, through burning coal, oil and gas. This adds to the power of the greenhouse effect, making the planet even warmer.
Many scientists believe that, if the warming is not stopped, there will be huge climate changes. The sea level could rise by one metre this century.
Should this come true, millions of homes would be swallowed up by the sea and the world will be flooded with" climate refugees" looking for somewhere else to live.
We can infer from Paragraph 2 that             .

A．Tuvalu is in danger of being swallowed up by the sea

B．all Tuvalu islands are about five meters above the sea level

C．drinking water in Tuvalu has been destroyed

D．Tuvalu is often flooded by storms and waves

The author uses Tuvalu and Venice as examples in order to explain           .    

A．it is first places sinking into the sea

B．it is sinking into the mud where they stand

C．it will disappear in the future

D．its trouble is caused by global warming

What does the underlined word "refugees" (in the last paragraph)mean?

A．People forced away from their homeland

B．Sudden changes caused by world climate

C．Animals closely connected with weather

D．Bad effect of climate changes

Which of the following is NOT true according to the text?

A．The main cause of global warming is human pollution

B．The average global temperature has risen by 1-3℃over the past century.

C．The warmer temperature causes the sea level to rise

D．There will be huge climate changes unless the warming is stopped