4. Number the steps 1 st, 2 nd and 3rd.

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Pollen lands on the stigma

A sperm cell fuses with an egg in the ovule.

A pollen tube grows down through the style to the ovary.

Steps are given below.

1) Pollen lands on the stigma of the flower.

2) A pollen tube grows down through the style to the ovary.

3) A sperm cell fuses with an egg in the ovule.

Explanation:

First the pollens fall from anther of the male part on the stigma of the female part of the flower. After that, the pollen reached to the ovary through pollen tube. Then the sperm cells of male combine with the egg of female forming a zygote (seed).