If a cloud has ice crystals in its upper part and liquid droplets in its lower part, what is the main reason?

Correct answer: Temperature decreases with height

Direct answer: C, temperature decreases with height. A cloud can extend through different altitude levels. In the lower, relatively warmer part, water can remain in liquid droplets. In the upper, colder part, the temperature may be at or below the freezing point, so some water becomes ice crystals. Thus the vertical temperature difference explains the two forms of water in the same cloud. A is wrong because clouds contain water in vapour, liquid, or solid form; moisture is necessary. B is wrong because a cloud is made of tiny water droplets and ice particles, not rock. C is correct because rising altitude usually brings lower air temperature, allowing ice to form above while droplets remain liquid below. D is wrong because ocean salinity does not directly determine the phase of water inside a cloud. Memory cue: higher and colder often means ice; lower and warmer often means droplets.