Which of the following statements regarding angiosperms is incorrect?

The correct answer is Option (1) → The megaspores formed from the megaspore mother cell are diploid.

In the ovule, the megaspore mother cell (MMC) is diploid and divides by meiosis, so the four megaspores formed are haploid. In most flowering plants one of them is functional and develops into the female gametophyte (embryo sac).

Option (1) The megaspores formed from the megaspore mother cell are diploid. — An incorrect statement. The megaspores are formed by meiosis of the megaspore mother cell, so they are haploid, not diploid.

Option (2) The pollen grains represent the male gametophytes. — A correct statement. Pollen grains are the male gametophytes of flowering plants.

Option (3) In a majority of flowering plants, one of the four megaspores is functional and develops into the female gametophyte. — A correct statement. One megaspore is functional while the other three degenerate; this is monosporic development.

NCERT Extract:
The Pistil, Megasporangium (Ovule) and Embryo Sac – “… The MMC undergoes meiotic division. … Meiosis results in the production of four megaspores (Figure 1.8a). Female gametophyte : In a majority of flowering plants, one of the megaspores is functional while the other three degenerate. Only the functional megaspore develops into the female gametophyte (embryo sac).”
Stamen, Microsporangium and Pollen Grain – “… Pollen grain: The pollen grains represent the male gametophytes.”