Cobalt chloride paper is blue when dry but turns pink with water. Blue cobalt chloride paper was fastened to the upper and lower surfaces of a plant leaf. After 20 minutes, many small pink dots were observed on the paper on the lower surface, and a few pink dots were seen on the upper surface. What conclusions can be drawn?

I. There are more stomata on the lower surface than on the upper surface.
II. Stomata on the upper surface are blocked by the waxy cuticle.
III. More transpiration occurs through the lower surface than through the upper surface.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

B