In the following question, out of the given four alternatives, select the one which best expresses the meaning of the given word.Obligatory

The correct choice is option A.Obligatory means required by a legal, moral, or other rule; compulsory or essential.Necessary means required to be done, achieved, or present; needed, making it the closest synonym.Optional and Voluntary are antonyms of obligatory.Liberalized means to become less strict.