Which of the following is not a ground for divorce under the Hindu Marriage Act, 1955?

Section 13(1)(ii) of the Hindu Marriage Act, 1955 makes it a ground for divorce that the respondent has ceased to be a Hindu by conversion to another religion. But under Section 2(1)(b) the Act applies to Buddhists, Jains and Sikhs as well, so a Hindu who becomes a Buddhist does not cease to be a Hindu for the Act. Hence "Respondent a Hindu converting to Buddhism." is not a ground for divorce.

The others are grounds: renouncing the world by entering a religious order (Section 13(1)(vi)), venereal disease in a communicable form (Section 13(1)(v)), and, for a wife, the husband being guilty of sodomy since the marriage (Section 13(2)(ii)). (Leprosy, once a ground under Section 13(1)(iv), was omitted by the Personal Laws (Amendment) Act, 2019.)