Which statements explains something that the fossil record indicates? Earth is 4.5 billion years old Mammals have always existed on earth Mass extinctions have occurred several times on earth The amount of water on earth has decreased over time

Consider the following planned experiment. factor experimental group control group light exposure tots of sun tots of sun amount of water weekly weekly type of soil nutrient rich nutrient rich size of pot large which variable is being tested in this experiment? small a. size of pot b. type of soil c. light exposure d. amount of water