It's a fine day. The White family get up at seven o'clock. They have breakfast at seven forty. And then they go to the park. They take a basket of food and a carpet（地毯）. The park is not far from their home, so they ride bikes there. Then they get to the park, it's half past eight. Mr. and Mrs. White are talking with each other. Their son, ted, is playing with a ball. Their daughter, Jenny, is taking photos.
After about an hour, Ted and Jenny sit down to relax. At that time, they see a squirrel eating a pine nut（松子）in a big tree. When they see the squirrel eating, they feel hungry（饥饿的）. They go to help their parents take the food out of the basket. Ted has a hamburger. Hamburgers are his favorite food. Jenny has an apple. Mr. and Mrs. White have some bread. They have a great time in the park.
的定义域为R，且
的取值范围是 （ ）
