When teaching the difference between vowels and consonants it is important to point out that the former is characterized by

• A. Free airflow through the vocal tract
• B. Obstructed airflow through the vocal tract
• C. Nasal resonance
• D. Voicing only

Answer: (A)

The main idea here is that vowels are produced with an open, unobstructed vocal tract, so the air flows freely from the lungs through the mouth. This open passage lets the vocal cords vibrate (usually) and the tongue and lips shape the resonances in the oral cavity to create different vowel qualities. That open airflow is what distinguishes vowels from many consonants, where some part of the vocal tract is narrowed or blocked to create different sounds.

So why this option fits best? Because the defining feature of vowels is that the airflow faces no significant obstruction, allowing the vocal tract to act as a resonator and produce the vowel’s characteristic sound. The other features describe things that can occur with some sounds but aren’t universal to vowels: obstructed airflow is typical of many consonants, nasal resonance occurs with nasal sounds or nasalized vowels, and voicing is a property that can apply to both vowels and consonants, not a defining feature of vowels.