xMerrie is pointing to the fact that the verb "beantwoorden" is transitive, whereas "antwoorden" is intransitive.
This is actually the function of the "be-" prefix in Dutch: it indicates that the verb is acting on a direct object, thus making it transitive.
Ik woon. = I live (as in reside).
Ik bewoon het huis. = I inhabit the house.
Ik jaag. = I hunt.
Ik bejaag hem. = I hunt after him.
I antwoord. = I answer.
Ik beantwoord hem. = I answer him.
Ik loop. = I walk.
Ik beloop het tapijt. = I walk on the carpet.