As you learned in part b, a non-burning helium core surrounded by a shell of hydrogen-burning gas characterizes the subgiant stage of stellar evolution. as time goes on, the star continues to evolve, and eventually, it becomes a red giant. rank the stages a star goes through as it evolves from a subgiant into a red giant, from latest to earliest. a) the shell of hydrogen surrounding the star's non-burning helium core ignites. b) pressure in the star's core decreases. c) pressure from the star's hydrogen-burning shell causes the non-burning envelope to expand. d) the star's non-burning helium core starts to contract and heat up. e) the star becomes a red giant. f) the surface of the star becomes brighter and cooler.

E- The star becomes a red giant (LATEST STAGE)

F- The surface of the star becomes brighter and cooler

C- Pressure from the star's hydrogen-burning shell causes the non burning envelope to expand

A- The shell of hydrogen surrounding the star's nonburning helium core ignites.

D- The star's non burning helium core starts to contract and heat up

B- Pressure in the star's core decreases (EARLIEST STAGE)

(A star moves away from the main sequence once its core runs out of hydrogen to fuse into helium. The energy once supplied by hydrogen burning reduces and the core starts to compress under the force of gravity. This contraction allows the core and surrounding layers to heat up. Finally, the hydrogen shell around the core becomes hot enough to ignite hydrogen burning.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.