Question

Which best describes the purpose of a controlled experiment?
to make sure the results of the experiment support the hypothesis
to prevent a dangerous condition resulting from a reaction
to examine whether one variable causes a change in another
to prevent an undesired change in a variable

Answer 1

to examine whether one variable causes a change in another

A controlled experiment isolates and manipulates an independent variable while keeping other variables constant to test for a causal effect on the dependent variable.