Answer: Option B) They are chemical reactions that give off energy and increase the temperature of the surroundings.
Step-by-step explanation:
Exothermic reactions are chemical reaction that occurs spontaneously and brings about the release of energy (in form of heat) to raise the temperature of their surroundings. Hence, the reacting vessel feels hot as the reaction proceeds to completion.
An example of exothermic reaction is the reaction between an acid and base