28. The leaves of submerged or floating plants have adapted to aquatic environments. Taking the floating leaf of a water lily as an example, what is the distribution characteristic of its stomata? (A) Stomata are primarily distributed on the lower (abaxial) epidermis. (B) Stomata are primarily distributed on the upper (adaxial) epidermis. (C) The stomatal density is roughly the same on both the upper and lower epidermis. (D) It has no stomata at all.