Ⅰ．阅读理解
The immense and forbidding Southern Ocean is famous for howling winds and strange waves that have tested mariners for centuries．
But its true strength lies beneath the waves．
The ocean's dominant feature, extending up to two miles deep and as much as 1，200 miles wide, is the Antarctic Circumpolar (极地附近的) Current, by far the largest current in the world．
It is the world's climate engine, and it has kept the world from warming even more by drawing deep water from the Atlantic, Pacific and Indian oceans, much of which has been in the deep ocean for hundreds of years, and pulling it to the surface．There, it exchanges heat and carbon dioxide with the atmosphere before being pushed again on its endless round trip．
Without this action, which scientists call upwelling, the world would be even hotter than it has become as a result of humancaused emissions of carbon dioxide and other heattrapping gases．“From no perspective is there any place more important than the Southern Ocean，”said Joellen L．Russell, an oceanographer at the University of Arizona．“There's nothing like it on Planet Earth．”
For centuries this ocean was largely unknown, and its conditions were so extreme that only a relative handful of sailors went to its waters with lots of icebergs．
What fragmentary scientific knowledge was available came from measurements taken by explorers, naval ships, the occasional research expeditions or whaling ships．
But more recently, a new generation of floating, autonomous probes (探测仪) that can collect temperature, density and other data for years — diving deep underwater, and even exploring beneath the Antarctic sea ice, before rising to the surface to phone home — has enabled scientists to learn much more．They have discovered that global warming is affecting the Antarctic current in complex ways, and these shifts could complicate the ability to fight climate change in the future．
1．Why does the true strength lie beneath the waves in the Southern Ocean?
A．There is the deepest current in the world．
B．There is the world's largest current．
C．There is severe cold climate in the South Pole．
D．There are the strongest winds and strangest waves．
2．How does the Southern Ocean keep the world from warming even more?
A．By pushing severe cold water to the other oceans．
B．By cooling the warmer water from the other oceans．
C．By drawing cold water from other oceans and pulling it to the surface．
D．By keeping cold water in the other oceans for hundreds of years．
3．What does the underlined word “fragmentary”mean in Paragraph 7?
A．Advanced． B．Abstract．
C．Incomplete． D．Concrete．
4．What do scientists discover according to the last paragraph?
A．The current there is in normal condition despite global warming．
B．The current there is under the complicated influence of global warming．
C．The autonomous probes have found solutions to global warming．
D．Nothing can be done for global warming due to severe cold climate．
