The correct answer is: b) M. Singaravelar.
M. Singaravelar was a social reformer and politician who founded the Madras Labour Union in 1918. The union was one of the first trade unions in India and played a significant role in the fight for workers’ rights.
B.P. Wadia was a businessman and politician who was involved in the Indian independence movement. He was not involved in the founding of the Madras Labour Union.
Periyar E.V. Ramasamy was a social reformer and politician who was known for his work on caste reform and women’s rights. He was not involved in the founding of the Madras Labour Union.
Rettamalai Srinivasan was a social reformer and politician who was known for his work on education and social welfare. He was not involved in the founding of the Madras Labour Union.