Which of the Following Statements Describes a Controlled Experiment

Multiple Choice

Which of the following statements describes a controlled experiment?

A) an experiment that is repeated many times to ensure that the results are accurate
B) an experiment that proceeds at a slow pace to guarantee that the scientist can carefully observe all reactions and process all experimental data
C) an experiment with at least two groups,one of which does not receive the experimental treatment
D) an experiment with at least two groups,one differing from the other by two or more variables