An experiment in which only one variable is changed is a (an) experiment.

Answer;

D. controlled

An experiment in which only one variable is changed is a controlled experiment.

Explanation;

-A control experiment is an experiment where the researcher only changes one variable at a time in order to isolate the results.

In a controlled experiment, most conditions are constrained so that they do not change. One or two other conditions are then changed and measured by the experimenter. These are known as the independent variables.

For example; An experiment where all subjects involved in the experiment are treated exactly the same except for one deviation.

the statement is true