B)
Because it flows. I dunno about you, but that sounds like a liquid to me! Sorry if i'm wrong.
Answer: Independent variable is what is being modified, it is important to compare it to your control group, (which is the original).
Dependent variable is what is being measured, to compare it to the control group to see if your hypothesis works or not.
Explanation: Here's a(n) example:
Bob wanted to take a mint with a mint drop, and he wanted to measure if it can make his breath fresher, but he also wanted to take it with a regular mint to see which is the freshest breath.
Independent variable: Mint drop.
Dependent Variable: Breath (To see if it is going to change with a mint drop.)
Control Group- Regular mint.
Its gone be b cause the organism can produce them out
Studies of populations that reveal correlations between dietary habits and disease incidence are epidemiological studies.
I believe those are both non-contact forces bc it's not something physical