The sentence suggests that children can understand meaning through words visually without needing to hear the sounds. The correct term here is "audible," which refers to something that can be heard. It implies that even if the sounds are not heard, meaning can still be gained.
Option (A), aural, refers to something related to hearing, but it is often used in contexts involving perception or listening, which doesn't fit the sentence as precisely as "audible."
Option (C), vocal, refers to the act of producing sound with one's voice, which is not the focus here. The sentence is talking about the meaning of words without needing sound, not about the production of sound itself.
Option (D), intelligible, refers to something that is understandable, which is close but doesn’t directly address the absence of sound, making it less appropriate than "audible."
Thus, option (B) is the most accurate choice.