The correct answer is: c) 1891.
The Naga Hills are a mountainous region in northeastern India. The region was inhabited by various Naga tribes for centuries. In the 18th century, the British East India Company began to expand its influence into the region. In 1826, the British signed a treaty with the Ahom kingdom, which gave the British control of the Naga Hills. However, the British did not formally annex the Naga Hills until 1891.
The annexation of the Naga Hills was met with resistance from the Naga tribes. The Nagas fought a series of wars against the British, but they were eventually defeated. The British ruled the Naga Hills as a part of Assam until 1947, when India gained independence. After independence, the Naga Hills became a part of the Indian state of Nagaland.
The Naga Hills are a beautiful and diverse region. The region is home to a variety of plant and animal life. The Naga people are a proud and independent people. They have a rich culture and history. The Naga Hills are a fascinating and important part of India.
Option a) is incorrect because the British East India Company signed a treaty with the Ahom kingdom in 1826, which gave the British control of the Naga Hills. However, the British did not formally annex the Naga Hills until 1891.
Option b) is incorrect because the British did not formally annex the Naga Hills until 1891.
Option d) is incorrect because the Naga Hills became a part of the Indian state of Nagaland in 1947.