Which answer defines exothermic reaction?
a. a process in which energy is released as heat
b. a process in which energy is absorbed as heat
c. a process in which energy is stored and released
d. a process in which energy is not present in a system

The answer which  defines  exothermic  reaction is

a process  in which  energy  is released as heat ( answer A)

 Explanation

 Exothermic reaction  is a chemical reaction in which  energy is released into environment in form of heat.

For example  of exothermic reaction

Is a combustion reaction such as lighting a candle whereby  oxygen react with wax to produce carbon (iV)  oxide, water and heat.

i think it is true since you can test the answer and can use observations to complete it.