& for the conclusion just restate the intro, PLEASE HELP

After cloud droplets form, what must happen to them for precipitation to occur?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

Inside a flashbulb, oxygen surrounds a thin coil of magnesium. when the flashbulb is set off, a chemical reaction takes place in which magnesium combines with oxygen to form magnesium oxide. which of the chemical equations matches the reaction above? a. mg + o2 mgo2 + energy b. 2mg + o mg2o + energy c. 2mg + o2 2mgo + energy d. mg + o mgo + energy