Answer:
The answer to your question is letter a. exothermic reaction.
Step-by-step explanation:
a. an exothermic reaction An exothermic reaction is a reaction that gives off heat, so this option is correct.
b. an endothermic reaction An endothermic reaction is a reaction that absorbe energy from the surroundings so this option is wrong.
c. absorption reaction It's a reaction similar to an endothermic reaction so is not the right answer
d. precipitation reaction It's another kind of reaction where one of the products precipitate, this option is incorrect.