Though President Nixon expanded the war in Vietnam into Laos and Cambodia, his administration pursued

a policy of Vietnamization, which

Though President Nixon expanded the war in Vietnam into Laos and Cambodia, his administration pursued  a policy of Vietnamization, which aimed at reducing the number of American troops in the war.

Explanation:

Vietnamization refers to the doctrine of President Richard Nixon from the time of the Vietnam War, according to which US forces would gradually withdraw from Vietnam and leave the defense of South Vietnam to the Vietnamese. At the same time, America would send modern weapons, equipment, advisers and financial aid to South Vietnam to compensate for the departure of their troops.  

The first American troops began to leave Vietnam at the end of 1969, and the withdrawal was completed by 1973. South Vietnamese forces, reinforced with American weapons and equipment, carried out attacks on the North Vietnamese hinterland in Cambodia and Laos in 1971, but suffered heavy losses. As a result, many experts strongly questioned South Vietnam's defense capabilities, but the US withdrawal continued nonetheless.  

Following negotiations in Paris, a ceasefire was agreed, where the Americans pledged to cease military action, cease aid to South Vietnam, and gradually withdraw their forces from South Vietnam.

d. the right to establish a one-house legislature