The best unit to measure the length of an object is meters.
Answer: Option A
Explanation:
Length is defined as the distance covered by any object from one end to another end of the object. It can also be termed as single dimension of the object. It is a measuring variable and like all measuring variables, it also has SI unit. The SI unit to determine the length of any object is meter.
So among the given options, cubic meters can't be the correct unit for length because it has three dimensional variable while length is a single dimensional variable. Similarly, kilograms is the unit of weight or mass of any object and kilogram per cubic meter is for density of any object. Thus the best unit for measuring the object's length is meters.