Which of the following sets of data should not be displayed with a pie chart?

a. the percentage of people who support a new speed limit law and the percentage of people who oppose the new speed limit law
b. the percentage of people who speak only one language and the percentage of people who speak multiple languages
c. the percentage of workers with college degrees and the percentage of workers without college degrees
d. the percentage of people who have a full-time job and the percentage of people who have a part-time job