Which unit would you need fewer of to measure a tree?

You would need fewer the unit kilometer (km) to measure a tree.

Explanation:

In the internet you can find that the greatest height of a tree is aobut 115 meters.

Thus, you would never expect to find a tree measuring kilometers or miles.

If you used kilometers as unit, the measure of the tallest tree woul be about 0.115 km (115 meter divided by 1,000).

Most of the trees meausre in the range of 1 to 20 meters. That would be 0.001 km to 0.020 km.

Thus, kilometer is not a unit that you would need to measure a tree. You'd rather use centimeters, when the tree is small, and meters for most of the trees. You may also use feet, since 1 meter is about 3.28 feet, or even yards, since 1 yard is equal to 3 feet.