What is the best reason for the scientific community to accept a theory?

The answer for #3 is c but i don't know why

Read these sentences from the text. near the equator, the tropics receive the most rain on a consistent basis. as a result, the fresh water falling into the ocean decrease the salinity of the surface water in that region. [. .] . . as the salt content of sea water increases, so does its density. what can you infer about how rain affects the density of surface water near the equator?

Agas occupies 475 cm^3 at 313k. find its volume at 367k. you must show all of your work to receive credit. be sure to identify which of the gas laws you will be using