_______ are produced without blocking or constructing the passage of air.

• A. Consonant sounds
• B. Diphthongs
• C. Glottal stops
• D. Vowel sounds

Answer: (D)

The key idea here is how the airstream is shaped during sound creation. Vowel sounds come from an open vocal tract—the air flows freely through the mouth or nose while the sound is formed by the shape of the tongue, lips, and jaw. There’s no significant obstruction or closure in the airway, which is what keeps vowels distinct from many other sounds.

This is why the statement points to vowel sounds as the ones produced without blocking or constricting the passage of air. Consonants involve some degree of narrowing or closure in the vocal tract, and glottal stops, in particular, require a momentary blockage at the glottis. Diphthongs are still vowels, just more complex vowel sounds that glide from one vowel quality to another, and they keep the airway open throughout.

So, the best choice is vowel sounds because they represent sounds produced with an open, unobstructed airflow.