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.

Option (d) is the correct answer.

Explanation:

A test or experiment in which only one variable is changed at a time in order to verify the result is known as a controlled experiment.

That is only independent variable need to be adjusted with respect to the dependent variable.

Thus, we can conclude that the action to test a piece of treated iron and a piece of untreated iron under the same conditions would be most important to perform in a controlled experiment in the given situation.

c is the answer because when something is left after something evaporates that shows the chemical change.