Ascientist wants to perform a controlled experiment to test the effect of rust on chemically treated iron. which action would be most important to perform in a controlled experiment? design an experiment that is based on previously published results. expose the treated iron to the corrosive effects of the air. test a large piece of treated iron and a small piece of untreated iron. test a piece of treated iron and a piece of untreated iron under the same conditions.

Test a piece of treated iron and a piece of untreated iron under the same conditions.

Explanation:

A controlled experiment is the one where a control variable is used. A control variable is the one which does experience any test in the experiment. Instead it is kept as a standard benchmark for comparison with the variables used in the experiment.

According to the given situation, Test a piece of treated iron and a piece of untreated iron under the same conditions. is the correct option because in this a tested sample that is treated with a chemical agent is used along with a piece of untreated iron under the same conditions. This will give indication of the affect of treatment on the iron under conditions which can cause rust.