Step 1: Background.
The first major international conference on the environment was the United Nations Conference on the Human Environment, held in Stockholm, Sweden, in 1972.
Step 2: Analyzing the options.
(A) 1972: Correct — Stockholm Conference.
(B) 1985: Incorrect.
(C) 1992: Refers to Rio Earth Summit.
(D) 1995: Incorrect.
Step 3: Conclusion.
The first world summit for environmental protection was held in 1972.