Sometimes C papers are grammatically and stylistically fairly strong but their content is very weak and general. A good paper. It may have some grammatical errors but not many, and usually not serious ones. It may have some stylistic problems, but not so much that they disrupt the reading of the essay. The thesis will be articulated clearly and supported throughout the paper.
B papers are enjoyable to read.
Virtually NO grammatical errors or stylistic problems, but the paper will also impress reader with its clarity, development, and insight. You may revise your papers. I may specifically ask you to, but if not, you may still turn in a revision. Always return the earlier copy too. I'll re-grade the paper and retain only the revision's grade.