Answer:
d. millimeters
Explanation:
The kilometer is the largest of the units here. The size order of the units are
1 millimeter<1 inch<1 feet<1 kilometers.
Letters are generally very small in size so the best unit to measure the dimensions would be millimeter
The length in inch can be converted to millimeter as
1 inch = 25.4 mm
The length in feet can be converted to millimeter as
1 feet = 304.8 mm
The length in kilometer can be converted to millimeter as
1 km = 1000000 mm.
