The correct answer is: C. 23rd June, 2014
The Great Himalayan National Park is a national park in the Indian state of Himachal Pradesh. It was established in 1974 and is the largest national park in the state. The park is home to a variety of wildlife, including snow leopards, Himalayan tahr, and musk deer. It is also home to a variety of plant life, including rhododendrons and oaks. The park was inscribed as a UNESCO World Heritage Site in 2014.
Option A is incorrect because the Great Himalayan National Park was not inscribed as a UNESCO World Heritage Site on 23rd June, 2013.
Option B is incorrect because the Great Himalayan National Park was not inscribed as a UNESCO World Heritage Site on 20th May, 2014.
Option D is incorrect because the Great Himalayan National Park was not inscribed as a UNESCO World Heritage Site on 23rd May, 2014.