The correct answer is letter A. The disk soaked in distilled water is the controlled variable because it is the only differential factor from all of the other variables which are all disinfectants. Controlled variables are elements that are not changed throughout the experiment. When something is unchanged it is better for scientists to analyze the relationships of other variables better.
Answer:
Im confused on what you mean
Explanation:
Energy is needed to cause a change in the state of matter because adding energy to matter causes a physical change as matter moves from stage to another.
Astronomers use an effect called parallax.
Answer:
yes
Explanation:
an example being finches from the Galapagos
