Answer:
D. Lavinia will win because Lydia received a legal benefit
Step-by-step explanation:
In this case, Lavinia is the promisee, since Lydia (the promisor) promised to give her $10,000 if she stopped smoking. Lavinia incurred in a legal detriment when she stopped smoking, simply because she has the smoke if she wants to. Personally, I consider smoking a bad habit, but anyone that smokes is free to do so as long as they comply with the law. A legal detriment is always paired with a legal benefit, even if the action doesn't actually result in a tangible benefit to Lydia.