Step 1: Historical background.
International Women’s Day was officially recognized by the United Nations in 1975, which was also celebrated as International Women’s Year.
Step 2: Analyzing the options.
(A) 1975: Correct — UN began celebrating International Women’s Day in 1975.
(B) 1978: Incorrect, no such declaration was made this year.
(C) 1980: Incorrect, though women’s rights movements continued strongly.
(D) 1985: Incorrect, too late.
Step 3: Conclusion.
Therefore, International Women’s Day was officially announced in 1975.