题目

—What does your sister do? — _____. A . She's my friend. B . She is Ok C . She's teaching D . She's a teacher 答案：D19．已知⊙O的半径r=$\sqrt{3}$，圆外一点P到圆心的距离PO=2，则两条切线PA、PB的夹角的度数是120°．