Polution is one of the biggest reasons
Answer:
The answer is C.
Explanation:
In experimental research, the independent variable is unchanging and may or may not have an effect on the dependent variable (in this case, the test scores). For this reason, idependent variables are also called explanatory variables.
An easy way to remember the difference is that <u>independent variables change the outcome of dependent variables. </u>
I believe the answer is slavery.
