Step 1: Grounds for Divorce Under Hindu Marriage Act.
The Hindu Marriage Act provides specific grounds for divorce, including mental disorder, venereal disease, and incurable unsound mind. These grounds are specified under Section 13 of the Act.
Step 2: Explanation of Other Options.
- (A) Mental Disorder is a valid ground for divorce under the Hindu Marriage Act.
- (B) Venereal Disease in communicable form is a ground under Section 13(1)(v) of the Act.
- (C) Incurable Unsound Mind is another valid ground under Section 13(1)(iii).
- (D) Living separately for less than three months is not a ground for divorce; it requires a separation period of at least two years.
Step 3: Conclusion.
The correct answer is (D), as living separately for less than three months is not a valid ground for divorce.