If the question is asking you all except which, the answer is "people fled the urban centers because they had become too crowded and unsanitary"
Anti-war marches and other protests, such as the ones organized by Students for a Democratic Society (SDS), attracted a widening base of support over the next three years, peaking in early 1968 after the successful Tet Offensive by North Vietnamese troops proved that war's end was nowhere in sight.
