Question

experiments
variables
in all experiments, it is important that everything except the independent variable stay constant.
because of this, with several changing variables, we can not determine which variable caused the
result.
when everything except the independent variable stays constant in an experiment, it is termed a
\controlled experiment.\ doing a controlled experiment is important to determine the cause of
observed changes.
what should be held constant in a controlled experiment?
everything except the control group
everything except the independent variable
everything except the dependent variable

Explanation:

In a controlled experiment, the goal is to isolate the effect of the independent variable. By keeping all other factors (variables) constant, any changes in the dependent variable can be attributed to the independent variable. The text on the left - hand side of the image also emphasizes that in an experiment, everything except the independent variable should stay constant.

Answer:

everything except the independent variable