阅读下列短文，从每题所给的四个选项（A、B、C、D）中，选出最佳选项。Dear Miss Manners，
When an ice cube melts, it creates a puddle (水坑). When an ice sheet (冰盖)melts, it raises sea levels. It sounds simple, but scientists have debated for decades whether both the Antarctic and Greenland ice sheets actually were shrinking, and how much that melting contributed to rising sea levels.
Now, a new study has provided the best evidence of how the polar ice sheets are responding to our warming world. In the study, An international team of scientists looked at 20 years of' data in the ice sheets collected by 10 satellite missions. The team's conclusion: The Greenland and Antarctic ice sheets both are losing ice overall. The researchers also found that between 1992 and 2011, meltwater from those shrinking ice sheets caused sea levels to rise by about 11 millimeters.
Over the 19 years studied, the Greenland ice sheet lost 2.7 trillion metric tons of ice. The Antarctic ice sheet also shrank by about l.3 trillion metric tons. Previously, some scientists disagreed whether the Antarctic sheet, the largest mass of ice in the world, was shrinking or growing or neither.
