A marble dropped in still water will create circular ripples or waves. The radius of each circular wave will increase 4 centimeters per second. What is the circumference of the circle after t seconds?

The radius grows at 4 centimeters per second, so after t seconds the radius is r = 4t centimeters. Circumference is C = 2πr, so C(t) = 2π(4t) = 8πt centimeters. Therefore, the correct choice is C, C(t) = 8πt.

AI-written and checked against the verified answer.