1 . When Joseph Cook first landed on the Greenland ice sheet in 2010, he was expecting to see a primitive white environment. What he found was "colorful mix"-from blacks and grays to greens, purples and browns, with blue streams cutting through the ice. the rainbow colors Cook encountered are created by a collection of tiny life forms that reproduce on the surface of the ice sheet. Biodiversity is usually considered a good thing, but in this case the abundance of tiny life is speeding up ice melt, and likely causing global sea levels to rise faster than scientists have predicted

Cook says the tiny life forms he studies are contributing to the problem. One of these organisms is an algae(海藻) that grows in the thin layer of water on the surface of the ice. it produces purple-brown- pigment(色素) which acts “like a natural sunscreen, "says Cook, protecting the algae from the full force of the Arctic sunlight. The pigment also causes the ice to heat up and melt.

“If you go out on a hot day wearing a black T-shirt, you get warmer than if you go out on a hot day wearing a white T-shirt. The same thing happens on the ice," says Cook. "These algae, like the black T-shirt for the glacier, are causing it to warm up in the sun and melt faster.”

Cook’s research on a part of the Greenland ice sheet covering 3, 900 square miles revealed that algae is responsible for up to 13% of the ice melt. In some localized areas, the algae boosted melting by up to 26%.

Glacier algae are not a new phenomenon-there are records of them in the diaries of polar explorers from the 1870s, says Cook. What's becoming clear is that ice sheets are surprisingly dynamic and complex environments. "There are so many questions to answer, "says Cook. "It's kind of like a theme park for a scientist because there's just so much to do.

1. What is quickening the ice melt?

A．The algae.	B．Human activities.
C．Global warming.	D．Blue melt streams.

2. Why is the example of wearing a black T-shirt mentioned?

A．To clarify a rule.	B．To explain the phenomenon.
C．To add humour.	D．To make a conclusion.

3. What can we infer from the last paragraph?

A．Scientists will avoid exploring polar regions.

B．Cook feels proud of the current results.

C．A theme park will be built on ice sheets.

D．There's a long way for research into ice sheets.

4. From which is the text probably taken?

A．A news review.	B．A travel brochure.
C．A geography textbook.	D．A science magazine