Final answer:
In an experiment, you should only have one B)independent variable, which is the factor manipulated to observe changes in the dependent variable, while control variables are kept constant.
Step-by-step explanation:
In an experiment, it is best practice to only have one independent variable. The independent variable is the factor that the experimenter manipulates to observe its effects on the dependent variable, which changes in response.
Control variables must also be present to ensure that they do not influence the outcome of the experiment.The independent variable in an experimental study is crucial because it is the only important difference between the experimental and control groups.
It allows researchers to measure the effects of this variable on the dependent variable, while control variables are kept constant to prevent them from affecting the results.
For instance, in a plant growth experiment, scientists might vary the amount of fertilizer given to plants (the independent variable) to observe its effect on plant growth (the dependent variable) while controlling other factors such as water, light, and temperature.