Question

as human populations increase, more shelter is needed. increasing shelter often requires making a trade - off with another resource. in which case is a food resource decreased to increase a shelter resource?
farmland is converted into house lots.
old - growth timber is cut to build houses.
corn is made into ethanol for cars instead of food.
wind power generated on farmland provides electricity for a factory.

Explanation:

• Farmland is converted into house lots: Farmland is a food - related resource. When it is converted into house lots (a shelter - related use), food production potential (a food resource) is decreased while shelter (housing) is increased. This is a direct trade - off between food (farmland) and shelter (house lots).
• Old - growth timber is cut to build houses: Old - growth timber is a natural resource (related to forest ecosystems). While it is used for building houses (shelter), it is not as clear a trade - off with another major resource category (like food) as the farmland case. Forests have multiple functions (biodiversity, carbon sequestration etc.), but the question is about a trade - off with a major resource category (shelter vs. another).
• Corn is made into ethanol for cars instead of food: This is a trade - off between food (corn as food) and energy (ethanol). It is not a trade - off with shelter.
• Wind power generated on farmland provides electricity for a factory: This is a trade - off between food production (farmland) and energy (wind power for factory electricity). It is not a trade - off with shelter.

Answer:

Farmland is converted into house lots.