Which conditions are necessary for rain to form?

A necessary condition to the formation of precipitation is that the air becomes saturated with water vapor. Saturation is the first step in the formation of precipitation (i.e. it is necessary but not sufficient). pressure. Air becomes saturated if RH is 100%.

A necessary condition to the formation of precipitation is that the air becomes saturated with water vapor Moist air must cool down for water to release in liquid form

i would say b. research typically uses a variety of sources

i dont know sorry why dont you looking it up on google