For each variable which you listed, explain how you will stop this variable from changing. These are your control variables.

I'm sorry, but you didn't provide any specific variables to control. However, I can give you a general idea of how to control variables in an experiment.

1. Constant Environment: If the environment can affect the variable, you should keep the environment constant. For example, if you're testing plant growth, you should keep all plants in the same location with the same light and temperature conditions.

2. Same Equipment: Use the same equipment for all measurements or observations. Different equipment may have different levels of accuracy or precision.

3. Same Procedure: Follow the same steps in the same order every time you perform your experiment. This includes the way you handle materials, the way you measure, and the way you record data.

4. Randomization: If there are variables you can't control, use randomization to reduce their impact. For example, if you're testing the effect of a drug on humans, you can't control all aspects of the participants' health and lifestyle. But you can randomly assign participants to the treatment or control group, which should average out any differences between groups.

5. Replication: Repeat the experiment several times to ensure that your results are not due to chance. This can also help you identify and control for unexpected variables.

Remember, the goal is to ensure that the only thing changing in your experiment is the independent variable, the one you're testing. All other variables should be kept constant, or controlled.