Active transport requires energy because it usually involves the movement of OA.
substances from an area of high concentration to an area of low concentration.
ОВ.
substances from an area of low concentration to an area of high concentration.
OC.
substances that can easily pass through the cell membrane, such as water.
OD
substances in the gas phase, such as oxygen and carbon dioxide.

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.

c is the answer. hope this