According to Figure 11.3, which of the following is true of third party and independent candidates on U.S. House district ballots since 1992?

a. There have been more third party and independent candidates than in the past.
b. There have been less third party and independent candidates than in the past.
c. The level of third party participation has remained constant with past levels.
d. Many districts have actively discouraged third party and independent candidates.
e. All districts have had at least one third-party or independent candidate since 1992 .

a