Final answer:
The nasal flutter test is used to identify problems with nasal emission, which is when air escapes through the nose during speech. This test helps assess the functioning of the velopharyngeal mechanism.
Step-by-step explanation:
The nasal flutter test is used to identify certain speech disorders related to the resonance of sound in the nasal cavity. By fluttering the nose while sustaining the /i/ and /u/ vowels, the test helps identify problems such as nasal emission, which is when air escapes through the nose during speech.
In this particular test, if a pulsing change in the acoustic signal is heard, it indicates a problem with nasal emission. This can be caused by structural issues or weaknesses in the velopharyngeal mechanism, resulting in a floppy or insufficient closure of the soft palate and the back of the throat.
Therefore, the correct option is (d) Nasal emission.