Which action would be most important to perform in a controlled experiment? ___A.

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

Explanation:

A controlled experiment is defined as an experiment where the experimenter or the researcher tries to test or experiment his result by changing one variable at a time and keeping the other factors under the same conditions and sees how it effects the result.

The factors which can be changed in an experiment is called its variables.

In the context, testing a piece of treated iron as well as a untreated piece of iron under the same working conditions forms a controlled experiment.

There are different kinds of conductors, most notably electrical and thermal conductors. But they are often inclusive of each other (electrical conductors are typically good thermal conductors). A conductor transmits something through its body with high efficiency while an insulator does not transmit very well. In the case of electricity, a conductor transmits electrical energy between two points while an insulator blocks the flow of electricity. Two examples of conductors are copper and silver. Two examples of insulators are wood and styrofoam.