Which of the following is correct for aquatic plants?      

(a) All aquatic plants use water for pollination.   

(b)  Not all aquatic plants use water for pollination.

(c) Vallisneria flowers are pollinated by water under the water surface. 

Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons.  Not all aquatic plants use water for pollination. In a majority of aquatic plants
such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants.