If it's just one grade and the rest of your transcript is strong, they may not even ask about it (then again, they may, some interviewers are a**holes). If they do ask about it, UseUrHeadFred is right: take responsibility for what happened. Don't trash the professor who gave you the grade or make ridiculous excuses. One exception would be if you were sick when you took the MCAT or something like that...if you have a legitimate reason, explain it, but don't make excuses for yourself. If you do decide to say that the reason for your low grade is that you just weren't able to manage time efficiently, I'd make sure to point out how you've learned from that experience and that you're much better at time management now. In med school, you WILL be busy...and you will be taking four or five couses at a time that are as demanding as orgo or biochem. Time is at a premium, and time management skills are essential, so if you don't have them now would be a good time to learn. This is what my pre-med advisor told me when I came in complaining about my ability to memorize everything in biochem...that when I was in med school I'd have four or five courses just like biochem and have to be able to memorize it all...so better get a handle on it now if med school was what I wanted. Best advice I got in the process. I didn't like it at the time, but he was right.
