Answer:
Meters
Explanation:
Meter is the standard unit of length in SI system and is normally used to measure houses and fields, therefore it is appropriate unit of measure for the dimensions of the playground.
A meter has 100 centimeters which is fairly small unit and cannot be used for dimensions of playground.
Similarly a Kilometer has 1000 meters and is used to measure long distances from one place to other which also makes it inappropriate unit for dimension of playground.
Hope that clarifies the answer.