I just bombed this test and i have 1 retake left. please help!!

the products have more energy than the reactants

Explanation:

endergonic reactions require energy to be driven, and therefore the change in gibbs free energy is a positive change, due to the energy gained.

the answer to your question is:

c. complementary base-pairing

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.