During an experiment, a student observes the formation of a precipitate. why does this indicate that a chemical reaction is likely occurring

A. A solid forms, and there is a change of color.

a boiling water reactor does not boil the water. a pressurized water reactor boils the water faster. a pressurized water reactor is heated directly by the core. a pressurized water reactor does not use fission.

it's c (engineer's do their work with mechanical stuff not on any living being)