A、People move together. B、It is getting harder to travel in winter. C、There are more ways of travelling. D、It is less dangerous

Climate change has altered the lives of Native Alaskans in the state’s interior in dramatic, sometimes dangerous ways. Although the effects of change are well documented along the coast, where higher tides and fierce storms have threatened native communities,(32)a study by the US Geological Survey(USGS)has found native people in Alaska’s interior also have felt the transformation to a warmer climate during the past several decades of their lifetimes. The study, appearing in the October 2011 issue of the journal Human Organization, is a rare, but increasingly common kind of research that tried to match the "traditional knowledge" of people at the site—hunters and village elders—with scientific data. "They pretty much agreed," said Nicole Herman-Mercer of the USGS in Boulder, Co. All of the subjects remarked that the weather has been warmer in recent years, most notably in the winter. Temperatures once commonly fell to minus 40 degrees Fahrenheit for days. Now if they sink that low. it is for shorter periods of time.(33)"The weather also has become less predictable," the men said, "as well as more dangerous." People also saw a change in the populations of animals in the area, important to hunters.(34)Ptarmigan(雷鸟)and ducks have disappeared, while beaver(海狸)and moose(麋), not seen before in that part, are now common. Changes to the area’s rivers are even more extreme.(35)Frozen rivers are the highways that link communities in the winter and the ice is now almost half as thick as they remember it, making travel more difficult and considerably more dangerous.
32. What is the purpose of the study conducted by the US Geological Survey?
33. What is the change of the weather in Alaska?
34. What is the change in animals in Alaska?
35. What is the result of the change of frozen rivers?