Why Are Third Parties Referred to as the Unsung Heroes

Why are third parties referred to as the unsung heroes of American politics?

A) They eliminate the difference between the major and minor parties.
B) They help the major parties win elections by splitting their votes.
C) They have lasted longer than the two major parties.
D) They provide a major economic benefit to the country.
E) They bring new issues to the forefront of public debate.