Step 1: Understanding the Question.
Under Section 11 of the Hindu Marriage Act, marriages that violate specific provisions of the Act are considered void. These include bigamy, degrees of prohibited relationships, and child marriage. However, the concept of a sapinda relationship is a specific restriction within the Act related to marriage.
Step 2: Conclusion.
Sapinda relationship is a ground for voidable marriages (Section 5 of the Hindu Marriage Act) but not for void marriages under Section 11. Therefore, option (C) is the correct answer.