How is the nitrogen cycle important to humans?
It produces free nitrogen that humans can breathe
It converts nitrogen into a form that humans can obtain by eating other organisms
It produces nitrogen compounds that humans can breathe
It converts nitrogen into a form that humans can obtain by absorbing it through it through their skin

It converts nitrogen into a form that humans can obtain by eating other organisms

Explanation:

The answer is B (just took the test)

Explanation:

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.