How does vaccination work?
antibodies from donated blood are injected into the body.
a strong form of the disease is injected under the skin.
o a weakened form of the disease is inhaled through the nose.
medication that fights the disease is injected into the bloodstream.

A strong form of the disease is injected under the skin.

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.