Because of categorical perception:

Question

Quizplus · Accepted Answer

Categorical perception refers to the phenomenon where slight acoustic differences between two stimuli are perceived as distinct and discontinuous categories. This means that we experience a sharp boundary between two phonemes, such as the /b/ and /p/ sounds. While slight differences may be detected, they are not perceived as different phonemes, which rules out option A. Option B is also not accurate, as not all pairs of speech sounds are easily discriminated based on acoustic differences alone. Therefore, option C is the best choice.

Because of Categorical Perception