A coin is flipped 25 times, and we would like to know the probability that 15 or more of those flips are heads side up.

A geometric distribution models the number of trials needed to get the first success. Here, the 25 flips are a fixed number of trials, and we want the probability of getting at least 15 heads among them—not the waiting time until the first head. So the geometric distribution is not appropriate; choice C is correct.

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