参考答案

正确答案：BC
解析：The professor discusses how glaciers are created: You might expect that heavy snowfall is the main requirement for the formation of a glacier; For a glacier to form, the snow can't melt. The professor also discusses the movement of glaciers: ...part of the ice moves over the edge of the hollow and starts moving down the valley. Large glaciers usually move faster than small ones. Also, the movement is faster in the summer...; Most valley glaciers move at a rate of... (2.1)