Final answer:
A voiceless stop is only aspirated at the beginning of a syllable, which is typically the case for the voiceless stops /p/, /t/, and /k/ in English.
Step-by-step explanation:
A voiceless stop is aspirated only at the beginning of a syllable. In phonetics, aspiration refers to a strong burst of air that follows the release of a consonant. In English, voiceless stops, namely /p/, /t/, and /k/, are typically aspirated when they occur as the first sound in a stressed syllable. Aspiration is not used when these consonants are immediately followed by a vowel within the same syllable or when they occur in syllable-final positions. Therefore, the correct answer is C) Only at the beginning of a syllable.