Correct Answer : Option (D) - CTBTO
Note : CTBTO (The Comprehensive Nuclear-Test-Ban Treaty Organisation) offered India an 'Observer' status and an access to International Monitoring System (IMS) data. CTBT is a global treaty that runs IMS which constantly monitors the Earth for nuclear explosions and shares evaluative findings with its member states. CTBTO's headquarters is in Vienna, Austria. Currently, IMS has 337 facilities, located in 89 nations. India wants CTBT to have a clause on complete nuclear disarmament and didn't yet sign the treaty as CTBT favours 5 nuclear weapon states, namely, China, US, Russia, France and UK.