In floating leaved plants, stomata occur on.
A. Lower surface
B. Upper surface
C. Both surfaces
D. Absent

Hint: Stomata are the tiny structure which bears pore on the leaf. Such a structure is necessary to maintain the plant homeostasis by releasing water and oxygen from it and taking carbon dioxide. Stomatal pores are surrounded by the two guard cells, subsequently epidermal cells.

Complete answer:
Stomata are the important structure of the plants which are present on the leaf which maintain the plant body temperature by transpiration process and help in exchange of gases. Opening and closing of stomata are maintained by the turgor pressure in the guard cell which is influenced by the presence of sodium and potassium ions. Stomata perform transpiration in the influence of sunlight.

In most of the plants’ stomatal structure are present in the lower surface of the leaf, but in case of floating aquatic plant stomatal structure is present on the surface of the leaf to show transpiration properly, but in case of submerged aquatic plants, they may lack such structure completely.

Lower surface - stomata are present on a leaf on its lower surface in most of the plants and their number may vary according to its adaptation and environment and plant variety or group, except aquatic plants.

In xerophytes plant stomatal numbers are low to reduce and they may not open during day time and open at night, due to less precipitation and water availability.

Hence, the correct answer is option (B).

Note: Different type stomata are found depending on size, structure and arrangement of the subsidiary cell around the guard cell, like, in dicots actinocytic, anisocytic, anomocytic, diacytic. In monocots, gramineous, hexacyclic, tetracytic. In ferns, hypocytic, pericytic, desmocytic, pilocytic.