Final answer:
The teacher should inform the students that the words 'sudden,' 'velvet,' 'kitten,' 'napkin,' and 'contest' contain closed syllables, which have short vowel sounds.
Step-by-step explanation:
When continuing the discussion with the students, the teacher should inform students that each of the words presented in the lesson contains closed syllables. A closed syllable is when a syllable ends with a consonant, which results in the vowel having a short sound.
This is observed in the words 'sudden,' 'velvet,' 'kitten,' 'napkin,' and 'contest,' where each syllable contains one vowel followed by a consonant, making the vowel sound short. In contrast, a vowel digraph syllable contains two vowels that make one sound, a final stable syllable has a consonant followed by -le, and an open syllable ends in a vowel, typically resulting in a long vowel sound.