Step 1: Event Timeline Establishment.
- The Korean War (1950-1953) is the earliest event.
- SALT I, aimed at nuclear arms limitations, occurred in 1972.
- The NPT, designed to curb nuclear weapons proliferation, was signed in 1968.
- The Vietnam War (1950s-1975) followed the Korean War.
Step 2: Chronological Sequencing.
- (A) Korean War (1950-1953)
- (D) Strategic Arms Limitation Talks-I (1972)
- (C) Non-Proliferation Treaty (1968)
- (B) Vietnam War (1955-1975)
Step 3: Final Order.
The accurate chronological sequence is (2) A, D, C, B.