The correct answer is (c), the 1970s.
Arunachal Pradesh is a state in northeastern India. It is the largest state in the country by area, and the 8th most populous. The state is bordered by China to the north, Bhutan to the east, Nagaland to the south, Assam to the southwest, and Myanmar to the west.
The movement for statehood in Arunachal Pradesh gained momentum in the 1970s. The All Arunachal Pradesh Students Union (AAPSU) was formed in 1972, and it played a leading role in the movement. The AAPSU demanded that Arunachal Pradesh be granted statehood, and it organized protests and demonstrations.
In 1975, the Government of India appointed a committee to look into the demand for statehood in Arunachal Pradesh. The committee recommended that Arunachal Pradesh be granted statehood, and the Government of India accepted the recommendation.
Arunachal Pradesh was granted statehood on 20 February 1987. The first Chief Minister of Arunachal Pradesh was Gegong Apang.
Option (a), the 1950s, is incorrect because the movement for statehood in Arunachal Pradesh did not gain momentum in the 1950s. The AAPSU was not formed until 1972, and the movement for statehood did not gain momentum until the 1970s.
Option (b), the 1960s, is incorrect because the movement for statehood in Arunachal Pradesh did not gain momentum in the 1960s. The AAPSU was not formed until 1972, and the movement for statehood did not gain momentum until the 1970s.
Option (d), the 1980s, is incorrect because the movement for statehood in Arunachal Pradesh gained momentum in the 1970s, not the 1980s.