Concept:The given phonetic symbol represents the voiced ‘th’ sound, written as /ð/.
Explanation:The letters ‘th’ can be pronounced in two ways: voiced /ð/ as in “this”, or voiceless /θ/ as in “think”.
In the options, “northern” is pronounced /ˈnɔːðən/, so it clearly contains the voiced sound /ð/.
On the other hand, “bath”, “healthy”, and “teeth” all contain the voiceless sound /θ/, not /ð/.
Therefore, only the word “northern” matches the given sound.
Answer:A. northern