The correct answer is: a) Princely State.
A princely state was a state in India that was ruled by a prince or a hereditary ruler. The princely states were not part of British India, but they were under British suzerainty. This meant that the British had control over the foreign affairs and defense of the princely states, but the internal affairs of the states were left to the rulers.
Manipur was one of the princely states in India. It was ruled by the Maharaja of Manipur. The British had control over Manipur from the early 19th century until 1947, when India gained independence. After independence, Manipur became a part of the Indian Union.
The other options are incorrect. A colony is a territory that is ruled by another country. A protectorate is a country that is under the protection of another country. An independent ally is a country that is not under the control of another country.