Final answer:
The area of circle C in terms of π, given that the diameter is 6 cm, is 9π cm², which is option a).
Step-by-step explanation:
The formula A = πr², where r is the circle's radius and A is its area, can be used to determine the area of a circle. Given that the diameter d of circle C is 6 cm, the radius r would be half of the diameter, which is 3 cm. Plugging this value into the formula, we get A = π(3 cm)² = 9π cm². Therefore, the area of circle C in terms of π is 9π cm², which corresponds to option a).