Recently two of my seniors came to me with the same problem--they had D's and even if they aced the final exam, they couldn't get at least a C- in the course. And they need at least a C- in the course in order to be considered at California's 4-year universities.
If their grades were the result of lack of effort, I would consider this a lesson well learned and not think a thing of it. But I know both of them have tried and struggled all semester long. So I made them a deal: score at least a B on the final, so that I can have a high level of confidence that they've mastered a reasonable amount of the material, and despite their points earned I'll give them a C-.
I graded the finals. One was happy with the result, the other not so much--but I think I earned cool points from each of them just for providing that one last opportunity. Professionally, it's a decision I can live with.