Write down the units you would use to measure these lengths: the length of the river Ganga
Hence, the answer is km.
Write down the units you would use to measure these lengths: the length of your bedroom
Write down the units you would use to measure these lengths: the length of your little finger.
Write down the units you would use to measure these lengths: the height of Mt Everest
Write down the units you would use to measure these lengths: the diameter of your pencil