Answer:
Option c
Explanation:
In experimental design, there are lots of test to certify the essence of the design. When there exist an independent variable, every measure of control is applied to it to test if it measures the expectation ,so there can't be one or two control measure not applied to the independent variable, we have to test every respective attribute of the control measure, we have randomly apply different theories to see if the control measure with its independent variable meets standards that is why Option C is not a requirement