Valerie designed and conducted an experiment on pothos plants, which are common houseplants. Her hypothesis is that the direction of light will affect the growth pattern of a pothos plant. To test the hypothesis, she sets up two test groups of pothos plants and observes them three weeks later. The table summarizes the test groups and observations. Test Group Growth Conditions Observations
1 Light source is only
on the side of the
plant Stems and leaves
are bent toward
the light
2 Light source comes
from all directions Stems and leaves
are not bent

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 ligh