You need to gauge your own abilities and how you realistically expect to do on the remaining exams. If you have a 3.90, I bet you have the ability to pull off a "B." This would be best, obviously. If you don't think you can pull it off, consider withdrawing.
B > W > C at this stage in the game. Also keep in mind that with your history of academic success, none of those outcomes will keep you out of medical school.