The magnitude of electrostatic between two point charges separated by a distance r is f

qq/r2

I think this is correct answer

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d

conservation of mass

mass before something happens = mass afterwards