Select all the sources of the heat inside earth that are listed below.
a. mantle convection
b. earth's magnetic field
c. radioactive substances
d. lava on earth's surface
e. gravitational contraction
f. past bombardment by asteroids

Cpr, or cardiopulmonary resuscitation, is a first-aid technique to save lives. it involves compressions of the patient's chest cavity. which description is the best description of the functions of chest compressions in cpr? chest compressions are done to pump the heart. chest compressions are done to strengthen the rib bones. chest compressions increase carbon dioxide inhalation. chest compressions allow the patient's muscles to wake up.

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled

All phases of matter may have a fixed mass