Yadira has been walking for 30 minutes a day for the past 3 months. She is feeling better and wants to do more. There is a marathon in her town in a few weeks, so she is thinking that she should run in that. Is this an achievable goal? A. No, training for a marathon takes more than a few weeks. B. Yes, as long as she has a specific goal, she can accomplish it. C. Yes, she has been exercising so it should not be a problem. D. No, walking does not prepare her for anything but more walking.