Step 1: Understanding the Legal Change
The question asks which of the listed grounds is no longer a valid ground for seeking a divorce under various personal laws in India after the Personal Laws (Amendment) Act of 2019.
Step 2: Analyzing the Personal Laws (Amendment) Act, 2019
The Personal Laws (Amendment) Act, 2019 was enacted with the objective of removing leprosy as a ground for divorce from five different personal laws:
\begin{enumerate}
The Divorce Act, 1869
The Dissolution of Muslim Marriages Act, 1939
The Special Marriage Act, 1954
The Hindu Marriage Act, 1955
The Hindu Adoptions and Maintenance Act, 1956
\end{enumerate}
The amendment was passed to end the discrimination against persons affected by leprosy, in line with modern medical understanding that leprosy is now a curable disease and not highly contagious.
Step 3: Evaluating the Options
(A) Cruelty, (B) Desertion (misspelled as "Dissertation"), and (D) Mental Illness (of a certain specified nature) remain valid grounds for divorce under various personal laws.
(C) Leprosy: This has been specifically removed as a ground for divorce by the 2019 amendment.
Step 4: Final Answer
After the Personal Laws (Amendment) Act, 2019, leprosy can no longer be used as a ground for divorce. Therefore, option (C) is the correct answer.