Explanation:

1. The All India Trade Union Congress (AITUC) is the oldest trade union federations in India. It is not affiliated to any political party. According to provisional statistics from the Ministry of Labour, AITUC had a membership of 2,677,979 in 2002.
2. It was founded on 31 October 1920 with Lala Lajpat Rai as its first president in Bombay by Lala Lajpat Rai, Joseph Baptista, N. M. Joshi, Diwan Chaman Lall and a few others and, until 1945 when unions became organised on party lines, it was the primary trade union organisation in India. Since then, it has been associated with the Communist Party of India.
3. AITUC is a founder member of the World Federation of Trade Unions. Today, its institutional records are part of the Archives at the Nehru Memorial Museum & Library, at Teen Murti House, Delhi.
4. All the three politicians attended the All India Trade Union Congress meet.