A、Five dollars per mile. B、One dollar per mile. C、Thirty cents per mile. D、Twenty-five cents per mile. D细节题。男士提到，他目前所得到的最大数目的许诺金

W: Hey, Joe, haven’t seen you for months. Care for a drink at the bar?
M: I’d love to, but I’m already late for the talk about the benefits of walkathon this weekend.
W: Walkathon? What’s all this about?
M: Don’t you know?[13]Most of the residents in Packer Hall are going to try to walk the seven miles from the engineering library, across the campus and down to the city hall, in an effort to raise money for the new children’s hospital.
W: Sounds like a good idea. But I don’t understand where the money comes from.
M: Well, a few days before the walkathon, each participant goes around asking people to pledge just a certain amount of money for each mile that he or she expects to walk in the event. Then after the walkathon’s over, the participants go back to those same people, collect the money pledged and send it into the hospital.
W: So you mean if someone pledges, say, a dollar a mile, and you walk five miles, you can get five dollars?
M: That’s right. Of course, most of my friends aren’t such big spenders;[15]the biggest pledge I’ve gotten so far is 25 cents a mile.
W: And how many people have made pledges for you?
M: Eleven so far. Say, how about making it an even dozen?
W: Sure. If you do the same for me. The walkathon sounds like a perfect opportunity for me to break in my new pair of sport shoes.
12. Why does the man turn down the woman’s invitation?
13. What can we learn about the walkathon from the conversation?
14. What’s the purpose of holding the walkathon?
15. What’s the maximum pledge the man has gotten?