56.
The answer is: A
Explanation
The correct option is A: 18th May, 1955.
The Hindu Marriage Act, 1955 came into force on the same day it received the assent of the President of India, which was 18th May, 1955. This act was enacted to amend and codify the law relating to marriage among Hindus and others. It also included provisions for separation and divorce, which were not part of the traditional Hindu law. The act applied to all Hindus, Buddhists, Jains, and Sikhs, as well as to any other person who was not a Muslim, Christian, Parsi, or Jew by religion. The act was part of the Hindu Code Bills, which also included the Hindu Succession Act, the Hindu Minority and Guardianship Act, and the Hindu Adoptions and Maintenance Act.