Kenneth's parents own a cattle ranch. When they become too elderly to run the ranch by themselves, Kenneth moves back to the ranch to help them. With his parents' help and permission Kenneth builds a house on the ranch. After he builds it, his parents refuse to deed him the land. Kenneth can sue his parents under the doctrine of:

promissory estoppel

Explanation:

Based on the information provided within the question it can be said that in this scenario Kenneth can sue his parents under the doctrine of a promissory estoppel. This is a doctrine which prevents an individual/group from abiding to a promise, even if that promise was not made into a legal written contract. Such as is the case in this scenario since Kenneth's parents promised to deed him the ranch.

the correct answer is d