The answer is D. Remember that biology is the study of life.
I think the correct answer would be C. It would be restricting water and/or nutrients, instead of supplying ample quantities of both that would not change the results of the experiment. This is because you are still supplying the same amount of nutrients and other things needed by the plant so the ratio of the growth of the plants will still be the same.
I had this same question, so I believe I know what cladogram it is. If I am correct, the answer is that lizards and snakes are more genetically alike than lizards and birds. The cladogram shows that a common ancestor exists between these four vertebrates, but the statement that best explains the genetics showed by this cladogram is that lizards and snakes are more genetically alike than lizards and birds. Hope this helps! (: