读对话，选句子，补全对话。

A. But sometimes I go on foot. B. That's right. C. Why not? D. How do you usually go to school? E. What about you?

John: Good morning, Jack.

Jack: I usually go to school by bike.  I like walking.

John: Walking is good. Look at the sun. It's a fine day for walking today.

Jack:  And the air is nice and clean today.  Do you often go to school by bike?

John: Yes, but not today.

Jack:

John: My bike is broken（坏了）.