Suppose that an instructor assigns different letter grades based on points earned on a 10-point quiz, and that all scores have been verified to be between 0 and 10 inclusive. Also suppose that four possible letter grades can be assigned and that 9 or 10 points is an A, 7 or 8 points is a B, 6 points is a C, and 5 or fewer points is an F. To assign letter grades, the most efficient numeric array containing point values would contain __________ elements.

a. Ten

b. Five

c. Four

d. Three