Grasses show pollination by

The correct answer is Option (3) → Wind

Option (1) Water — Incorrect. Water pollination is rare and is seen mostly in aquatic monocots such as Vallisneria, Hydrilla and Zostera.

Option (2) Insect — Incorrect. Grass flowers are small, dull and without nectar or scent, so they do not attract insects.

Option (3) Wind — Correct. Grasses make large amounts of light, non-sticky pollen, have well-exposed stamens and feathery stigmas, and pack many flowers into an inflorescence. These are features of wind pollination.

Option (4) Animals — Incorrect. Animal pollinators such as birds and bats visit large, showy flowers, not grasses.

NCERT Extract:
Pollination – “… Pollination by wind is more common amongst abiotic pollinations. Wind pollination also requires that the pollen grains are light and non-sticky so that they can be transported in wind currents. They often possess well-exposed stamens (so that the pollens are easily dispersed into wind currents, Figure 1.10) and large often-feathery stigma to easily trap air-borne pollen grains. Wind-pollinated flowers often have a single ovule in each ovary and numerous flowers packed into an inflorescence; a familiar example is the corn cob – the tassels you see are nothing but the stigma and style which wave in the wind to trap pollen grains. Wind-pollination is quite common in grasses.”