Answer: The correct answer is an alcohol and an acid.
Step-by-step explanation:
Esters are defined as the functional group of organic compounds having general formula of
where R and R' are the alkyl or aryl groups. They are fruity smelling compounds.
It is formed by the combination of an alcohol and an acid.
For Example: The formation of ethyl ethanoate from the combination of acetic acid and ethanol.
The chemical reaction for the formation of ethyl ethanoate follows:

Hence, the correct answer is an alcohol and an acid.