Answer:
The only situation would the appropriate unit of measure be kilometers is option C.
Explanation:
Given the options we have to choose which would the appropriate unit of measure be kilometers.
Option A: The length of curtain
As curtain are not so much long which can measure in kilometers these are measure in meters. Therefore not considered.
Option B: The perimeter of a garden fence.
Generally, the gardens are of dimension is in feet or meter. The area of garden is less because these are small which results into the perimeter in feet or in meter.
Option C: The distance covered by a city's water pipes.
the distance between the two city is large thats why these are always measured in meters as kilometer contains thousands of meters.
Hence, correct option.
Option D: The amount of electricity used at a residence.
The amount of electricity used at a residence.
The basic unit of electricity is the Kilowatt hour (kWh).
Hence, never in kilometer.
The only situation would the appropriate unit of measure be kilometers is option C.