Question

Which two units you would use to measure population density?

Answer 1

Considering that the lesson is on density and density means human population in a certain area I would go with option C

Answer 2

You are measuring people and animals, so this is for sure two of your units. For the next units, you need to choose something big enough to hold a large number of these, so you would use square meters and acres. The answer is the third option: number of people per square meter and number of animals per acre