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 4t centimeters. Using the circumference formula C = 2πr gives C = 2π(4t) = 8πt, matching choice B.

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