Explanation:

V. V. Giri (Correct): Varahagiri Venkata Giri (1894–1980) was the fourth President of India (1969–1974). He was a prominent trade unionist and labour leader, serving as President of the All India Railwaymen's Federation and the All India Trade Union Congress. The V.V. Giri National Labour Institute (VVGNLI) is named after him, recognizing his contributions to labour welfare. V. Sanjeeva Reddy: He was the sixth President of India (1977–1982) and a politician, but not primarily a labour leader. K.R. Narayanan: He was the tenth President of India (1997–2002), a diplomat and academic, not primarily a labour leader. Zakir Hussain: He was the third President of India (1967–1969) and an educationist, not primarily a labour leader.