Please answer the following question: Read the following article and select the best answer. Article: The USA, New York--Whales and dolphins are facing increasing threats from climate change, according to a new report published by WWF and the Whale and Dolphin Conservation Society (WDCS). The report "Whales in hot water?" draws attention to the growing impacts of climate change on whales.They range from changes in sea temperature and the freshening of the seawater because of the melting of ice and increased rainfalls, to a sea level rise, loss of icy polar habitats and the _ of krill populations in key areas.Krill, a tiny shrimp that is dependent on sea ice, is the main source of food for many of the great whales. The speeding up of climate change adds greatly to trouble from other human activities, such as chemical and noise pollution, which kills some 1000 whales every day. "Whales and dolphins have an ability to adapt to their changing environment," said Mark Simmonds, International Director of Science at WDCS."But the climate is now changing at such a fast pace that it is unclear to what extent whales and dolphins will be able to adjust." Climate change impacts are currently greatest in the Arctic and the Antarctic.According to the report, cetaceans that rely on polar, icy waters for their home and food resources are likely to be greatly affected by the reduction of sea ice cover. WDCS and WWF are urging governments to cut global production of C02 by at least 50 percent by the middle of this century.The latest report of the Intergovernmental Panel on Climate Change showed it was possible to stop global warming if the world's emissions start to decline before 2015. Question: Which of the following is the most important for whales and dolphins? - Rainfall - Krill - Sea ice cover - High sea level
Answer:
Sea ice cover