Answer: The answer is C- comets!
Explanation: Callisto is composed mainly of rock and water ice, although other ices like ammonia ice and carbon dioxide ice may be present. Water ice occurs at the surface of Callisto so it would be comets.
Answer: transfer of heat by the actual movement of warmed matter
Explanation: convection is the process of heat transfer through fluids. When molecules absorbs heat they become excited and less dense causing it to rise.
Mass is always conserved in a physical change. Energy may be released or absorbed when a substance changes from one physical state to another. In a chemical change, a chemical reaction yields a completely new substance. A substance's particles are changed during a chemical reaction.