阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项，并在答题纸上将该选项标号涂黑。
A
Scientists have long understood the key role that oceans play in regulating the Earth’s climate．Oceans cover 70 percent of the globe and store a thousand times more heat than the atmosphere does．What’s newer is the understanding of how this key component of our climate system responds to global warming．
A brake on global warming—for now
One of the ocean’s most important climate functions is absorbing heat and carbon dioxide （CO2）, one of the gases that cause global warming．Acting as a heat sponge （海绵）, the oceans have absorbed huge amounts of heat and CO2 in the last forty years．
