Final answer:
The correct answer is d. the crops and the trees.
Step-by-step explanation:
When Luke sells his farm to Nina, and the contract does not specify otherwise, the sale typically includes both the crops and the trees. In real estate, when land is sold, it often includes all fixtures and improvements attached to the land, which would include mature trees that serve as windbreaks.
Crops, if they are growing and have not been harvested at the time of the sale, also typically convey with the property. This is based on the idea that these elements are integral parts of the farm's land and are not usually removed upon sale.