Crop Plants Can Have Higher Densities of Stomata on the Underside

Multiple Choice

Crop plants can have higher densities of stomata on the underside of their leaves than on the surfaces of their leaves. Some scientists hypothesize that that the evolution of this adaptation enhanced the ability of these plants to regulate the rate of CO₂ uptake for each surface.
-Suppose you wanted to test this hypothesis using sunflower plants. Which of the following would be the best procedure regarding the groups you use in your experiment?

A) Choose two equal-size groups of sunflower plants. One would be the experimental group and one would be the control group.
B) Choose equal-size groups of sunflower plants and zinnia plants. The sunflower plants would be the experimental group and the zinnia plants would be the control group.
C) Choose two groups of sunflower plants. The experimental group would have twice as many plants as the control group.
D) Choose two groups of sunflower plants. The experimental group would have half as many plants as the control group.