Chang knows one side of a triangle is 13 cm. Which set of two sides is possible for the lengths of the other two sides of this triangle?

For three lengths to form a triangle, the sum of any two sides must be greater than the third side. With sides 13 cm, 8 cm, and 9 cm, the two smaller sides add to 8 + 9 = 17 cm, which is greater than 13 cm, so these lengths can form a triangle. In each other choice, the two listed sides add to 13 cm or less, so they cannot form a triangle with a 13 cm side.

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