The correct option is B Must
Section 72 of the Indian Contract Law states, "Liability of person to whom money is paid, or thing delivered, by mistake or under coercion.—A person to whom money has been paid, or anything delivered, by mistake or under coercion, must repay or return it.' —A person to whom money has been paid, or anything delivered, by mistake or under coercion, must repay or return it."