For each of the following sets of data, determine whether the distribution of scores is unimodal, bimodal, or multimodal.

a. 4, 2, 11, 6, 10, 2, 6, 13, 2, 10, 6, 10, 1

b. 15, 17, 13, 18, 17, 14, 20, 18, 17, 14, 17

c. 20, 10, 50, 10, 80, 30, 70, 10, 60, 10, 80, 0, 30, 80, 10, 100, 80