Why is it necessary for the cores of high-mass stars to have a higher temperature than the interiors of low-mass stars

Which best term to describe a chemical reaction that absorbs energy from its surroundings? a.thermal conductor b.thermal insulator c.endothermic d.exothermic

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve

Only 3% of the water on earth is usable by humans. even though that 3% is through the water cycle, we still need to be careful not to waste water.