Final answer:
To demonstrate experimental control, you need to control the independent variables that are purposely manipulated or changed in an experiment, as well as the extraneous variables that could potentially influence the outcome of the experiment.
Step-by-step explanation:
To demonstrate experimental control, two sets of environmental variables that need to be controlled are the independent variables and the extraneous variables. The independent variables are the variables that are purposely manipulated or changed in an experiment. For example, if you are investigating the effect of temperature on plant growth, temperature would be the independent variable. To demonstrate experimental control, you need to control the levels or values of the independent variable.
On the other hand, extraneous variables are variables other than the independent variable that can potentially influence the outcome of the experiment. These variables need to be controlled in order to establish a cause-and-effect relationship between the independent variable and the dependent variable. Examples of extraneous variables in the plant growth experiment could be the amount of light, humidity, or soil composition. By controlling these variables, you can ensure that any changes in the dependent variable (e.g., plant height) are due to the manipulated independent variable (temperature) and not due to other factors.