Final answer:
The diagonal of the square inscribed in a circle with an area of 9π is 6.
Step-by-step explanation:
The student has asked a geometry question about the relationship between the area of a circle and the diagonal of a square inscribed within it. Given that the area of the circle is 9π, we must first find the radius of the circle. Since the area A of a circle is given by A = πr², solving for r gives us r = 3.
Because the square is inscribed in the circle, the diameter of the circle is equal to the diagonal of the square. Therefore, the diagonal d of the square is 2r, which is 2(3) = 6. This means the correct answer is b) 6.