In an experiment, the weight that mice gain is the dependent variable and the temperature of the environment is the independent variable. What must be held constant to obtain valid experimental results? A. the weight of the mice B. the color of the mouse cages C. the length of time that the mice are observed D. the temperature of the laboratory rooms

In the experiment, the weight that mice gain in different environment is analyzed. So, the weight of the mice is a variable that changes depending on the circumstances. Option A is eliminated. The color of the mouse cages is irrelevant to the experiment, because it has no impact on the weight that mice gain. Option B is eliminated. The length of time that the mice are observed must be constant for all experiments in order to obtain valid experimental results. All experiments should be done in the same period of time under different conditions. The temperature of the laboratory room is independent variable. This means that the weight that mice gain can depend on this variable. So, changing the temperature maybe will lead to different weight gain of the mice.