The graph shows the relationship between the length, x, in meters, of a pendulum and its period, y, in seconds. The period is the amount of time it takes the pendulum to swing forward and back. Which type of function best models the data in the graph?

For a pendulum of fixed gravity, its period increases in proportion to the square root of its length: T = 2π√(L/g). This means the period grows as the length grows, but not at a constant rate, so a square root function best models the relationship. The correct choice is square root.

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