After pollen lands on the stigma of a flower, which of the following happens first? Fertilization takes place.
An embryo grows inside the ovary.
The pollen grows a tube to the ovary.
The pollen units with an egg cell.

The pollen grows a tube to the ovary.

Explanation:

After pollen grains land on the stigma, a pollen tube grows from the pollen grain, through the style, and into the ovary. Sperm cells inside the pollen grain travel down the pollen tube and into the ovary which contains the ovules. Fertilization occurs when one of the sperm cells fuses with the egg inside of an ovule.

b - the respond is innate and varies over time.

good luck!