Choose the correct statement(s) regarding pollen grains.
I. Pollen grains are the male gametes of the flowering plant.
II. Pollen grain has a prominent two-layered wall.
III. The outer thick wall of pollen grain is called exine and the inner thin wall is called intine.
IV. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic materials known.

The correct option is B II, III and IV are correct
Pollen grains are male gametophytes of flowering plants which produce the male gametes.

Pollen grain has a two layered wall. The outer hard wall is called exine and the inner thin wall is called intine.

Exine is made up of a very resistant material called sporopollenin which can withstand high temperatures, strong alkali and acids. It cannot be degraded by any enzyme.

Hence statement I is incorrect and statements II, III and IV are correct.