Which of the following provides the best comparison between reptiles and fish?
a: they both have scales, but fish are ectothermic, and reptiles are endothermic
b: they are both ectothermic, but fish have gills, and reptiles have lungs
c: they are both vertebrates, but fish have three-chambered hearts, and reptiles have two-chambered hearts
d: they both lay eggs, but fish are invertebrates, and reptiles are vertebrates

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.