【正确答案】正确答案：A phoneme is a minimally distinctive set of sounds in a language that can signal a difference in meaning. It is an abstract phonological unit represented or realized by a certain phone in a certain phonetic context. A phone is an individual phonetic unit or segment that occurs in speech. The speech sounds we hear and produce during linguistic communication are all phones. Each of the set of phones which correspond to a single phoneme of a language is called an allophone. Phonemes are placed between slant lines (/ /) and phones are placed between square brackets ([ ]). Allophones of the same phoneme generally occur in different contexts and never distinguish one word from another. For example, when we pronounce the two words peak and speak, we are aware that the sound [ p ] is pronounced differently, in the word peak, the sound [ p ] is pronounced with a strong puff of air stream; but the same stop sound is pronounced slightly differently in the word speak, the puff of air is withheld a little. The [p] sound in peak is called an aspirated [ p ^h ] and the[p]sound in speak is an unaspirated[p ⁼ ]. There is a slight difference in the way they are pronounced, but such a difference dose not give rise to difference in meaning. So /p/is a phoneme in the English sound system, and it can be realized differently as aspirated or unaspirated in different contexts. The phoneme /p/ in English can be realized as aspirated [ p ^h ] and unaspirated [p ⁼ ], which are allophones of the phoneme /p/.