Final answer:
The increase in the price of dinners at fancy restaurants would cause the demand for babysitters to decrease as they are complements.
Step-by-step explanation:
The answer to this question is option d) Decrease; complements.
When the price of dinners at fancy restaurants increases, people are less likely to go out for dinner because it becomes more expensive. As a result, they would also be less likely to hire babysitters since they are usually needed when parents go out for dinner. This means that the demand for babysitters would decrease when the price of dinners at fancy restaurants increases.