Answer:
c. Control is needed to reduce the effects of confounding or extraneous variables on the variables being studied.
Explanation:
A control is an observation or an experiment is designed to reduced the effects of the variables other than the independent variables. This will increase the reliability of the results. It also reduces the confounding effects on the various variable that is being studied.
Hence the correct option is (c).
a) The tears of the goddess Isis
