Answer:
(A: Because of her advanced math skills and natural curiosity, Katherine is an outstanding student.)
The author's main point in this paragraph is to highlight Katherine's exceptional abilities and accomplishments as a student. The paragraph mentions several key events in Katherine's educational journey, including being selected to attend graduate school, advancing several grades in school, and graduating with the highest honors from college. These events all demonstrate Katherine's exceptional intelligence and dedication to her studies, and they help to paint a picture of her as an outstanding student.