单选题 Speaker A: If I were you, I'd ride a bike to work. Taking a crowded bus during rush hours is really terrible.
Speaker B: ______
A. Yeah, riding a bike is a healthful activity. Don't you think?
B. Yes, you're right. Buses are always very crowded during the rush hours.
C. Thank you for your advice. But my bike has got a flat tyre.
D. Certainly. I don't see why so many people go to work by bus rather than by bike.