The words far, for, purchase, and thirsty are examples of what?

The correct answer is that the words far, for, purchase, and thirsty are examples of R controlled vowel words. In R controlled vowel words, the vowel sound is influenced by the letter 'r' that follows it, resulting in a unique pronunciation that differs from typical vowel sounds.

In the words provided, the 'ar' in "far," the 'or' in "for," the 'ur' in "purchase," and the 'ir' in "thirsty" are all examples where the 'r' modifies the vowel sound. This modification creates a distinct phonetic pattern that is characteristic of R controlled vowels. Understanding this concept is crucial for recognizing how certain vowels behave when followed by 'r', which can aid in reading and pronunciation skills.