单选题 Bill: Hello, Mary. Why are you standing here in the cold wind?
Mary: ______, but buses are very full at this time of the day.
Bill: Where are you going? This isn't your way home.
Mary: But I'm not going home now. I'm going for a walk in the park.
A. I'm going home B. I'm going to work
C. I'm waiting for somebody D. I'm waiting for a bus