Answer:
C.Neither m nor n
Step-by-step explanation:
The control variable is the variables that might influence the response variable. We don't want a control variable to affect the response variable, so we keep the variable constant.
The response variable is the variable that we want to observe/measure. We won't manipulate or change the variable, we want to measure them. The variable we should manipulate is the explanatory variable.
Both variables shouldn't be changed, so the answer is C
