The correct answer is B) The United States pulled out and the North Vietnamese eventually took the entire country.
The United States got involved in the Vietnam War during the 1960's. The initial goal of getting involved was to ensure that South Vietnam did not fall under the control of the communist North Vietnam. This desire to stop communism from spreading was part of America's containment plan. The federal government wanted to stop the spread of communsim on a global scale, as government officials feared that if one country fell to communism, other countries close to it would fall as well.
Despite America's best efforts, they did not have much success overall in Vietnam. This is why Nixon called for the process of Vietnamization. This would result in South Vietnam taking over more of the fighting as the American forces withdrew. Ultimately, South Vietnam falls to the communist North Vietnam.
