Correct Option: A

The United Nations Conference on Environment and Development (UNCED), otherwise known as the Earth Summit or Rio Summit, was held in Rio de Janeiro, Brazil, in June 1992. An important achievement of the summit was an agreement on the Climate Change Convention. Besides, the Convention on Biological Diversity was opened for signature at the Rio Summiton 5 June 1992 and entered into force on 29 December 1993.