Pollination by water is seen inA. NelumbiumB. VallisneriaC. EichhorniaD. Nymphaea

Pollination by water is known as hydrophily. It occurs when water acts as a medium for the transfer of pollen from one flower to another. Let's examine the options:

A. Nelumbium (Lotus): This plant is known for being pollinated by insects (entomophily), not by water.

B. Vallisneria: Vallisneria is an aquatic plant that exhibits water pollination. Its flowers float on the surface of water, and the pollen is transferred by water.

C. Eichhornia (Water Hyacinth): This plant is typically pollinated by insects, not by water.

D. Nymphaea (Water Lily): Like the lotus, water lilies are usually pollinated by insects, not by water.

The correct answer is B. Vallisneria. This plant specifically relies on water for the transfer of pollen during its reproductive process.