Final answer:
The most appropriate metric unit for measuring the height of a giraffe is meters, as millimeters are too small and kilometers are for long distances, whereas meters suit the typical height range of a giraffe very well.
Step-by-step explanation:
Choosing the Appropriate Metric Unit for Measuring a Giraffe
When considering the metric units of length for measuring objects, it's important to select the unit size that best fits the object in question. In the case of measuring the height of a giraffe, the choices are millimeters, centimeters, meters, and kilometers. Millimeters are used for very small objects, which certainly does not apply to a giraffe. Kilometers are used for measuring long distances (about half a mile), far too large for our purpose. Now, considering that meters are roughly the size of a yard or wingspan, this would be the most appropriate unit to measure the height of a giraffe, which typically ranges from 4 to 6 meters in height for adult giraffes. Therefore, the answer would be 'B. Meters'.