The correct option is C IUCN
International Union for Conservation of Nature and natural resources (IUCN) is an international organisation established in 1948, which works in the field of conservation of nature and sustainable use of natural resources.
The main aim of this organisation is to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable.
IUCN Red list or Red Data Book was founded in 1994 as the world’s most comprehensive inventory of global conservation status of biological species. It maintains a Red Data Book or red list which is a catalogue of taxa facing risk of extinction.
United Nations Environment Programme (UNEP) is a leading environmental authority in the United Nations system responsible for coordinating responses to environmental issues within the United Nations system.
ICZN stands for International Code for Zoological Nomenclature, which provides and regulates a uniform system of zoological nomenclature ensuring that every animal has a unique and universally accepted scientific name.
WWF stands for World Wildlife fund now known as World Wide fund is a non-government organisation that works in the field wilderness preservation and the reduction of human impact on the environment.