The heir to a large estate will be of legal age within 30 days.

Comprehensive and Detailed Explanation (150–250 words):

Contracts entered into by a minor (a person not yet of legal age) are generally voidable at the option of the minor. In this case, the heir is still underage when signing both the listing and the sales contract. Although enforceable by the minor, they may be disaffirmed before reaching majority age or within a reasonable time thereafter.

Fulfilled (A) applies only once all terms have been performed.

Executed (B) means fully performed; here, the contracts are not.

Executory (D) means still in progress, which is true, but the critical legal issue is that the contracts are voidable due to minority.

Therefore, both contracts are voidable.