Kg is a different type, so that's not the answer. Km is used for measuring roads, so that's not the answer. Mm is too small, so that's not the answer. So the answer has to be D.
The answer is D because cm is the most appropriate measurement to measure a short distance. None of the other choices are appropriate to measure such small distances with. Millimeters are too small, kilograms is not a distance measurement, and kilometers are too huge of a distance measurement.
