简述IP电话的基本工作原理。
参考答案：
Sometimes Jim _____________ on Sunday. [ ]
A. plays basketball
B. plays the volleyball
C. playing basketball
D. play volleyball
正常人给予脂肪餐时胆总管扩张（）
A.正确
B.错误
C.是正常生理变化
D.是病理改变
