The correct option is D Contract is valid and A can recover the amount to the extent of assets of one lakh of rupees.
Under Section 68 of Indian Contract Law, 1872, 'Claim for necessaries supplied to person incapable of contracting, or on his account.—If a person, incapable of entering into a contract, or any one whom he is legally bound to support, is supplied by another person with necessaries suited to his condition in life, the person who has furnished such supplies is entitled to be reimbursed from the property of such incapable person.' Hence A can recover the amount to the extent of B's assets of Rupees One Lakh.