Astudent is investigating the effect of different salts on melting points. four patches of ice of equal size are roped off and a different type of salt is poured on each, one receives table salt (nacl), one receives calcium chloride (cacl2), one receives potassium carbonate (kco3) and the fourth receives inert sand instead. each patch receives an equal amount of salt or sand. the student measures the volume of ice remaining and subtracts it from the original volume of ice to see how much melted away. what is a control variable in this experiment? a. the type of salt applied to the ice. b. the size of the ice patches. c. the amount of ice that melted. d. none of these.

D. None of these.

Explanation:

A control variable is the one which remains untreated in an experiment. It is used for the purpose of comparision with the samples treated with a variable.

Here in the experiment, no control variable is used. As all the ice samples are treated with salts or sand and no one is left untreated.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.