Final answer:
The claim that U.S. major political parties have declined in membership since the 1950s is false; the Democratic Party has maintained consistent membership, and only the Republican Party has seen a slight decline. Hence option (b) is correct.
Step-by-step explanation:
The statement that both of the two U.S. major political parties have experienced a decline in membership and voter support since the 1950s is false. While the Republican Party has lost about 5 percent of its membership over the last decade, the Democratic Party's membership has stayed relatively constant. However, the number of self-identified independents has grown, indicating a shift in political identification rather than a general decline in participation in both parties.
It is also worth noting that the U.S. political landscape is characterized by the two-party system, with Democrats and Republicans being the dominant players. Despite this, there is an increasing call among Americans for the inclusion of a third party, with 58 percent of Americans expressing the need for more options beyond the traditional two-party system. This sentiment reflects a desire for a broader representation of views within the American political process.