Step 1: Understanding the Concept:
This question involves two key legal principles: the validity of a contract with a minor, and the liability of an endorser of a negotiable instrument (a cheque).
Step 2: Detailed Explanation:
1. Liability of the Minor (Drawer): Under the Indian Contract Act, 1872 (as established in the landmark case of \textit{Mohori Bibee v. Dharmodas Ghose}), an agreement with a minor is void ab initio (void from the very beginning). A minor has no capacity to contract. Therefore, the cheque drawn by the minor is void. The minor cannot be held liable on the cheque. So, options (A) and (B) are incorrect.
2. Liability of A (Endorser): A endorsed the cheque to X. Under Section 35 of the Negotiable Instruments Act, 1881, in the absence of a contract to the contrary, the endorser of a negotiable instrument is liable to every subsequent holder in case of dishonour of the instrument. When A endorsed the cheque to X, A implicitly guaranteed that the cheque would be honoured. Since it was dishonoured, A becomes liable to pay the amount to X. The fact that the drawer was a minor does not absolve the endorser of their liability.
3. Conclusion: X cannot sue the minor, but X can sue A, the endorser, who is liable upon dishonour.
Step 3: Final Answer:
The minor is not liable as the contract is void. However, A, as the endorser, is liable to the subsequent holder (X) upon the dishonour of the cheque. Therefore, X can enforce payment against A only. Option (C) is correct.