The argument that environmental change was a security issue pointed out for the first time in 1992 UN Conference on Environment and Development, which became popularly known as the Rio Earth Summit. The Earth Summit as the largest conference brought together more than a hundred state leaders and established the Commission on Sustainable Development, which provided the political basis for the concept of sustainable development. During the 1992 Rio Earth Summit conference, world leaders highlighted a number of environmental problems including biodiversity, the growing ozone hole, pollution, desertification, and climate change. Therefore, the correct option is A.