fertilizer is variable. It says that.
the others are controls
Ten plants are grown in equal amounts of sunlight with equal amounts of water and varying amounts of fertilizer. Sunlight, water, and fertilizer are
a) experiments b) systems c) variables d) controls
D
4 answers
It's asking what sunlight, water and fertilizer are
I told you
I agree with Damon; however, since neither c nor d can be correct, I think the answer must be b. The three together make a system.