A student needs to use the metric system while measuring the length of a box. Which units should he use?

It depends on the size of the box.

- - If it's one of the boxes printed on a sheet of graph paper,

then he should report the measurement in millimeters.

- - If it's the box that his new smartphone arrived in, then

he should probably use centimeters.

- - If it's the box that the new tractor was shipped to his

grandfather's farm in, then meters is the best unit.