Which chemical reaction supports the Law of Conservation of Mass?

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

Which of the following natural processes is most likely to support the formation of an underwater sinkhole? a pollution buildup from deposited minerals b limestone cave collapsing due to changes in sea level c erosion of large amounts of sand moved by ocean waves d oxidation of rock formed by chemical weathering

Which process transfers heat from inside earth to its surface? convection currents in mantle pulling away of tectonic plates drawing in of tectonic plates convection currents in crust