What are the roles of the two test groups in this investigation? A. Both are experimental groups, and each individually shows the effect of the direction of light. B. One is the experimental group and one is the control group, and together they show the effect of the direction of light. C. Both are control groups, but only Test Group 1 shows the effect of the direction of light. D. Both are experimental groups, but only Test Group 1 shows the effect of the direction of light.