The State of Hyderabad, located in the Deccan region of India, officially became a part of the Indian Union in the year 1948. Let`s understand each option:

Option 1: 1948. This is the correct answer. Known as the Operation Polo or the Police Action, it led to the annexation of Hyderabad into India in September 1948.

Option 2: 1950. This is incorrect. The Indian constitution did come into effect in this year, but Hyderabad had already acceded to India two years prior, in 1948.

Option 3: 1949. This is also incorrect. Some princely states did accede to the Indian Union in this year, but Hyderabad was not one of them.

Option 4: 1947. This is the year India gained independence from British rule. However, Hyderabad did not immediately accede to India in this year but remained an independent state until 1948.