The discussion on 'Sustainable Development' was started after submitting a report on environment to the United Nation in 1987. That report was

1. A

   First Report on Climate Change

   (a) First Report on Climate Change. IPCC’s First Assessment Report is 1990, not the 1987 UN environment report that opened the sustainable-development phrase in this question.

2. B

   Our Common Future

   (b) Our Common Future. The 1987 Brundtland Commission report to the UN, titled Our Common Future, defined sustainable development and started the global discussion named in the stem. Official key.

3. C

   Second Report on Climate Change

   (c) Second Report on Climate Change. IPCC SAR is 1995, eight years later and climate-specific, not the 1987 sustainable-development report.

4. D

   Fifth Assessment Report

   (d) Fifth Assessment Report. IPCC AR5 (2013–14) is decades after 1987.

Summary. Official key is (b) Our Common Future. Gro Harlem Brundtland’s WCED report (1987) went to the United Nations and made ‘sustainable development’ the policy idiom. IPCC assessment reports are a different, later climate series. Only Our Common Future matches the 1987 UN environment report in the question.