Answer:
C. a concern about the Vietnam War
Explanation:
In the late 1960s, the members of the counterculture share with many other American citizens the "concern about the Vietnam War."
The Vietnam war which lasted for about 20 years, beginning in 1955 and ended in 1975, saw the northern Vietnamese go against the South Vietnamese.
Then, with the American involvement lasting more than they had envisaged after committing themselves to take a side in the war, the counterculture movements and American society in general, joined together to express their desire to end the Vietnam War.