Which of the Following Analyses Is BEST Suited for a Scatter

Which of the following analyses is BEST suited for a scatter diagram?

A) A professor plots a student's exam score against the number of homework problems the student completed prior to the exam.
B) A professor determines a student's letter grade based on their final course average.
C) A professor determines the curve on the most recent exam by categorizing students into groups called A,B,C,etc.
D) A professor studies his student evaluations and classifies complaints into broad categories such as Assign More Homework and Make Exams More Challenging.