The correct answer is: 1946 AD.
The Himalayan Hill States Regional Council was formed in 1946 AD. It was a regional council of the princely states of the Himalayas. The council was formed to promote cooperation and coordination among the princely states. It also served as a forum for the discussion of common problems faced by the princely states. The council was dissolved in 1947 AD, after the independence of India.
Option A: 1934 AD is incorrect. The Himalayan Hill States Regional Council was not formed in 1934 AD.
Option B: 1939 AD is incorrect. The Himalayan Hill States Regional Council was not formed in 1939 AD.
Option C: 1940 AD is incorrect. The Himalayan Hill States Regional Council was not formed in 1940 AD.
Option D: 1946 AD is correct. The Himalayan Hill States Regional Council was formed in 1946 AD.