What was the one important factor that pass the 26th amendment in 1972 which lowered the voting age to 18?
a) the civil rights movement
b) the vietnam war
c) the women's suffrage movement
d) the korean war

Explanation:

Protest movements against the Vietnam War were happening during the 1960s, leading up to 1971 when the 26th Amendment was passed by Congress and ratified by the states.  Protests were especially common on college campuses across the country.  Part of those protests were the demands of young people chanting, "Old enough to fight, old enough to vote."  Since 18 was old enough to be drafted to fight in the war, young people argued for their right to vote as full citizens.

The 26th Amendment was passed by Congress on March 23, 1971.  It was ratified by the states faster than any other amendment, achieving ratification by July 1, 1971.

The 26th Amendment is worded as follows:  

Section 1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.

Section 2. The Congress shall have the power to enforce this article by appropriate legislation.