Ostriches have wings similar in form to those of their ancestors, but that do not allow the birds to fly.

their weight

Explanation:

Ostriches weigh more than 400 pound and can be as tall as 9 feetmaking it 99.9% impossible for its flight

Hope it helped?

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.