Answer:
C
(Perfect square)
Explanation:
Square root of 15 it will be 3.8..but doesn't repeat
Square root of 16 is 4 (perfect square)
Square root of 17 is 4.123... doesn't repeat or stop
Square root of 18 is 4.242.. but doesn't repeat or stop.
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A rational number can be expressed as a ratio or a fraction.
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16 can be expressed as a fraction the other numbers keep going meaning never stop.