In the evolution of extremely large stars, they begin as supergiants or supernovas, if the star nucleus is large enough it will continue to contract and form neutron stars, and finally, if the contractions continue, everything around the neutron star and the neutron star itself will be pulled into what is called a a. white dwarf c. giant b. nebula d. black hole

answer; /// i believe the correct answer is (reactants);

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.