Answer (a) — correct: In this diagram age meets the requirements to be a confounder because, as depicted in the diagram, age is a risk factor for breast cancer and is associated with pesticide use, but it is not a result of pesticide use.

Answer (b) — incorrect: This diagram illustrates that age is an intermediate in the pathway between pesticide use and breast cancer. If a factor is in the pathway between exposure and outcome, it is called a mediator.

Answer (c) — incorrect: In this diagram, age does not meet the necessary conditions for a confounder because it is not associated with the exposure.