Explanation:

- The Untouchability (Offences) Act was introduced to eliminate the practice of untouchability in India, making it a punishable offense.

- Option 1: 1955

- The Untouchability (Offences) Act was indeed passed in this year.

- It aimed to provide strict penalties for practicing untouchability.

- This enactment was a significant step towards social equality.

- Option 2: 1956

- This is incorrect as the act was passed in the previous year.

- Option 3: 1971

- This does not pertain to the passing of the Untouchability (Offences) Act.

- Option 4: 1950

- This year marks the adoption of the Indian Constitution but not the enactment of this act.

Option 1: 1955 is correct.