Pollen-pistil interaction is:

Which is incorrect statement?
I. Each cell of sporogenous tissue in anther is capable of giving rise to microspore tetrad.
II. The pollen grain represent male gametophyte.
III. Pollen grains are usually triangular and$10-15 \mu \mathrm{m}$ in diameter.

IV. Sporopollenin is one of the most resistance organic material which can be destroyed only by strong acids and alkali.

Examine the figure given below and select the right option giving all four parts $\mathrm{a}, \mathrm{b}, \mathrm{c}$, and $\mathrm{d}$.