Changes in pressure cause wind to blow.
River System........................
There is a close relationship between evaporation( transformation of water into water vapor in presence of heat), condensation (transformation of water vapor into water droplets), condensation nuclei (minute water droplet) and cloud (assemblage of too many water droplets). For the formation of cloud all these mentioned conditions are required.
Explanation:
Evaporation refers to the transformation of water into water vapor by the action of heat, condensation means transformation of water vapor into water droplet in normal temperature, condensation nuclei refers to the water droplets which is base of formation of cloud.
Cloud forms from the assemblage of water droplets. These water droplets are formed in saturated air condition when the air is full of humidity. Relative humidity means the ratio between the water holding capacity of air and the amount of actual water in air at that particular temperature.
The answer to your question is, Tank trucks marked with hazardous materials.
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