Which statement best describes the process of sexual reproduction?

a.
pollen is released with the aid of wind and water.

b.
a sperm cell fertilizes a vertebrate's egg cell, creating a zygote.

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c.
a mushroom ejects spores into the air even in the harshest conditions.

d.
a regular house fly begins as a maggot after budding.

B.  A sperm cell fertilizes a vertebrate's egg cell, creating a zygote.

Explanation:

Not A, because it is showing asexual production, in which, when the pollen lands, it will grow without needing of an opposite gender.

Not C, because it is exactly the same as A, in which it promotes asexual production.

Not D, because while sexual reproduction is needed, it does not give the process, rather, the process of life after being borned (you want an answer that gives the process before birth.

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answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.