The correct answer is (b) Labour Party.
The Labour Party was in power in the United Kingdom when India gained independence in 1947. Clement Attlee was the Prime Minister at the time. The Labour Party had been in power since 1945, and they had promised to grant India independence. They kept their promise, and India gained independence on August 15, 1947.
The Conservative Party was the main opposition party at the time. They opposed Indian independence, and they tried to block it. However, the Labour Party was able to pass the Indian Independence Act in 1947, and India gained independence.
The Liberal Party was a minor party at the time. They supported Indian independence, but they did not have much influence on the government.
The Socialist Party was not a major party at the time. They did not have any seats in Parliament, and they did not have any influence on the government.
In conclusion, the Labour Party was in power in the United Kingdom when India gained independence in 1947. Clement Attlee was the Prime Minister at the time. The Labour Party had been in power since 1945, and they had promised to grant India independence. They kept their promise, and India gained independence on August 15, 1947.