Explanation:

- Indian Labour Movement Overview:

- The labor movement in India began gaining momentum in the early 20th century.

- It was sparked by rising industrial activity and the need for improved labor conditions.

- Option Analysis:

- Option 1 (1875): Predates the organized labor movement; workers’ issues were not formally addressed then.

- Option 2 (1918): The correct year when the labor movement officially began with the formation of formal unions like the Madras Labour Union.

- Option 3 (1939): Significant labor activities occurred, but the movement started earlier.

- Option 4 (1945): Post-World War II era saw heightened activity, but not the start.

- The correct answer is 1918 from Option 2.