Final answer:
The question pertains to the concept of 'flexing' vowels in phonetics, which involves determining whether a vowel is pronounced as a short or long sound. For example, a short 'o' sound is presented in 'following,' and a long 'o' sound is found in 'enrolled'. The vowel's sound can sometimes be deduced from its position relative to certain consonants.
Step-by-step explanation:
The question asks about the vowel sound students learned to 'flex' in order to say a particular word. When considering vowel sounds, especially in relation to teaching students about phonetics and spelling, it's important to distinguish between short and long vowels. For example, a short 'i' as in 'brim' and 'mint' has a different sound than a long 'i' as in 'twine' and 'dive'. The same applies to the vowel 'o', where 'following' has a short 'o', and 'enrolled' has a long 'o'.
If the 'll' is at the end of a free stem, the 'o' right in front of it spells a long sound, but if the 'll' is in the middle of a free stem, the 'o' right in front of it spells a short sound. Similarly, the vowel sounds in front of 'tt' are short, as in the words with 'ttle' and 'tle'. Thus, understanding the position of letters can give clues to the vowel sounds.