Find an integer, x, such that 2, 4, and x represent the lengths of the sides of an acute triangle.

The sides must satisfy the triangle inequality, and for an acute triangle the square of the longest side must be less than the sum of the squares of the other two sides. With x = 4, the sides are 2, 4, and 4, and 4² < 2² + 4², or 16 < 20. Therefore, x = 4 works; the correct choice is C, 4.

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