The correct answer is D.
The antiwar movement was a movement against America's involvement in the Vietnam War.
Opposition to the United States involvement in the Vietnam War began with demonstrations in 1964 and grew into a big social movement over the next couple of years.
The protests centered themselves around college students first. Since students became involved in the Civil Rights Movements before, the anti Vietnam War protests became their protest against America's mainstream values and beliefs. They questioned America involvement in the war, thinking that the conflict was only of civil, domestic nature and America had no right to interfere. They condemned America's push for imperialism and they criticized the death of thousands of innocent people there. They were also very concerned about the environmental impact the war would have on Vietnam's nature.