Colin decided to investigate soil erosion by water. He measured rates of erosion on model hills made of soil, rock, and sand. Which of the following was the test
(independent) variable?

i just had a test on this with 2 attempts and got it wrong on both but i do know that the answer is not...

the steepness of the models hillside

or

the rate of erosion on the hills

so the answer is either...

the amount of water sprayed on the hills

or

the type of material used to construct the model hills

but i think its the amount of water sprayed on the hills...i hope i helped a lil ;)

Explanation:

c, liquids evaporate, creating a gas