Final answer:
The correct nasal phoneme heard in the word "long" is /ŋ/, represented by the letters 'ng' at the end of a word.
Step-by-step explanation:
The nasal phoneme you hear in the word "long" is /ŋ/.
Phonemes are the distinct units of sound in a specified language that distinguish one word from another.
For English, the nasal phonemes include /m/, /n/, and /ŋ/.
The /ŋ/ sound is often represented by the letters 'ng' at the end of a word, such as in "long", "sing", and "ring".
This is the sound that you hear at the end of the word "long", which makes option c, /ŋ/, the correct answer.