The distance between city A and city B is 22 miles. The distance between city B and city C is 54 miles. The distance between city A and city C is 51 miles.

The longest side is 54 miles. To classify the triangle, compare its square with the sum of the squares of the other sides: 22² + 51² = 484 + 2,601 = 3,085, while 54² = 2,916. Since 3,085 is greater than 2,916, the triangle is acute, so choice B is correct.

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