题目

The Arctic is home to over 21, 000 kinds of animals and plants. Two thirds of it is the Arctic Ocean. In winter, it is completely covered with sea ice. In summer, nearly 50 percent of these is ice. It’s also home to about 4 million people, a group of whom are Inuit. Jim is an Inuit boy. At 6:30 am, he wakes up and gets ready to go to school in his fur coat. It keeps him warm in the freezing weather. Half an hour later, he gets to school on a ski or snowmobile. Some of his friends go by car instead. At 11 :30 am, it’s time for lunch. There’s fish and other meat in his lunchbox. He sometim函数的定义域是（ ）A. B. C. D.