Organization responsible for maintaining Red Data Book is
A. IUCN
B. WWF
C. CITES
D. IBWL

Hint:-The Red Data contains information related to the endangered and rare species of organisms such as plants, animals and fungi. It contains detailed documentation regarding the different types of organism found in different habitats and their status as a group. The information present in the book allows it to be used for complete research and works related to conservation required for any species.

Complete step-by-step solution:-
The Red Data book is a documented detailed investigation and studies on the various types of species of living organism such as plants, fungi as well as animals in their local habitats. The book maintains a detailed investigation on the different species and they are grouped according to their population and occurrence in categories such as endangered, vulnerable species, rare species etc.
The data contained in the Red Data Book serves as a medium created for the identification, maintenance and protection of the species that are facing the threats of extinction or are at the verge of extinction. The several species are classified on the basis of colour coding which helps to identify the information in an easy way. The prescribed color coding is black, red, amber, white, green as well as grey. The black colour represents the species that are confirmed to be extinct and the red colour represents the species which are endangered at the present. The amber stands for those types of species which are considered as vulnerable and white represents the species that are rare. The green represents species that have recovered from endangered status and grey are the species about which the information is incomplete or under progress.
The Red Data Book is maintained by the IUCN or The International Union Of Conservation of Nature which has its headquarters in the United Kingdom. The institution produces a list of species which is known as the Red List of Threatened Species or the IUCN Red List. The IUCN is the world’s most important and comprehensive inventory regarding the conservation of the status of biological species. The institution is scientifically very rich and more advanced in the research and documentation of the species. The IUCN provides research on the status of the evaluation of the different species with the risk of extinction. It provides urgent information responses for immediate conservatory actions.
WWF or World Wide Fund for Nature is an international organization that works for the preservation of wildlife and reduction of impact of humans on the environment. It is the world largest conservation organization.
CITES or Convention on International Trade in Endangered Species of Wild Fauna and Flora is a treaty to protect endangered organisms including plants and animals. It is also known as the Washington Treaty. It works to ensure the protection in wildlife trading to protect the species.
 IBWL or Indian Board For Wild Life constituted by the Government of India to conserve and protect wildlife.
Therefore, the correct option is option A.

Note:- The Red Data Book is maintained and documented research investigation on several species that are classified into endangered, vulnerable and rare. The Red Data Book is maintained by IUCN. The IUCN is the world’ s largest institute for conservation and protection of wildlife and species.