单项选择题

John: I want to go to Chicago. When is the next train, please
Booking clerk: in fifteen minutes.
John: How much is the fare
Clerk: You want to buy a single fare or a round trip ticket
John: ______
Clerk: A round trip ticket saves you about 10% of the fare.

A. Will it take me straight there
B. How much is it
C. What’s the difference
D. What is the fare