C is correct answer
pi x r squared. If you have a computer, use the calculator function for the answer to your test question.
240mm=24cm,area of circle is radius squared x pi,radius=1/2 diameter so 12x12 =144 cm x pi(3.14)
is 452.16 so your answer is C ok.
how many cubic meters of cement are required to cover walkway 7 m long, 0.95 m wide and 10 cm deep