Final answer:
The promise Douglass made to give Krystal $1,000 for selling his house without a commission is not enforceable because it lacks consideration.
Step-by-step explanation:
The promise made by Krystal's friend Douglass to give her $1,000 in return for selling his house without charging a commission is not an enforceable contract because it lacks consideration. Consideration is an essential element of a contract and refers to something of value being exchanged between the parties involved. In this case, Krystal did not receive any benefit or consideration for selling the house without a commission. Without consideration, the promise is not legally binding.