The correct answer is (a) Bahurao V/s State of Maharashtra.
In the case of Bahurao V/s State of Maharashtra, the Supreme Court held that a Hindu husband converting to Islam and marrying again will be guilty of bigamy. The court held that the essential character of marriage under Hindu law is that it is a sacrament between two Hindus and that conversion to another religion does not dissolve the marriage. The court also held that the right to marry is a fundamental right under the Constitution of India and that this right cannot be taken away by conversion to another religion.
The other options are incorrect because they do not deal with the issue of bigamy. Option (b), Dr. A.N. Mukherji V/s State, deals with the issue of whether a Hindu can convert to Islam. Option (c), Sarla Mudgal V/s Union of India, deals with the issue of whether a Hindu woman can be forced to marry against her will. Option (d), P.V. Venkatraman V/s State, deals with the issue of whether a Hindu can be forced to undergo a religious conversion.