Which of the Following Best Describes a Controlled Experiment

Multiple Choice

Which of the following best describes a controlled experiment?

A) An experiment repeated many times to ensure that the results are accurate
B) An experiment includes at least two groups, one of which does not receive the experimental treatment
C) An experiment that includes at least two groups, one differing from the other by two or more variables
D) An experiment that includes one group for which the scientist controls all variables