The G77 was established to:

Correct option is A

The correct answer is a) represent Global South interests.
The Group of 77 (G77) at the United Nations is a coalition of developing nations designed to promote its members' collective economic interests and create an enhanced joint negotiating capacity on all major international economic issues.

Information Booster :
The Rise of the Global South
Established on June 15, 1964, by seventy-seven developing countries (signatories of the "Joint Declaration of the Seventy-Seven Countries"), the group emerged at the end of the first session of the United Nations Conference on Trade and Development (UNCTAD) in Geneva.

Voice of the Developing World: The G77 serves as the primary forum for the "Global South" to harmonize their views on global issues, ranging from trade and finance to climate change and poverty eradication.
Negotiating Power: By acting as a single bloc, these countries—which now number over 130 members—can balance the influence of the "Global North" (wealthy, industrialized nations like the G7) in international forums.
South-South Cooperation: Beyond negotiating with the North, the G77 promotes cooperation among developing nations in areas like technology transfer, trade, and shared infrastructure projects.