Final answer:
When interest rates increase, the demand curve for houses is expected to shift down.
Step-by-step explanation:
When interest rates increase, we would expect a demand curve for houses to shift down, so the correct answer is a) the demand curve will likely shift down. Higher interest rates make borrowing money more expensive, which reduces the number of people who can afford to buy houses. As a result, the demand for houses decreases, causing the demand curve to shift down.