Which of These Comments About a Team Member's Report Draft

Multiple Choice

Which of these comments about a team member's report draft is the least diplomatic?

A) I like the statistics that you provide in the introduction. I wonder if the audience will recognize these sources you consulted.
B) This introduction shows a lot of hard work. Perhaps an additional example would make your point even stronger.
C) You did not write this introduction very well. You left out a lot of important background information.
D) I know the proposal reviewers have very high standards. I think we all will benefit from improving our proofreading skills.