What Was the Final Outcome of the Vietnam War in Vietnam

What was the final outcome of the Vietnam War in Vietnam itself?

A) South Vietnam used a combination of American bombs and negotiation to persuade North Vietnam to retreat.
B) North Vietnam occupied Saigon,and the country unified.
C) Cambodian refugees joined the South Vietnamese army and helped to achieve a North Vietnamese presence in South Vietnam.
D) North Vietnamese troops flooded into South Vietnam and slaughtered millions of civilians.