Which statement about r-controlled vowels is true?

Which statement about r-controlled vowels is true?

• A. R-controlled vowels are vowels whose sounds are influenced by following 'r', as in 'car'.
• B. R-controlled vowels are a myth and do not exist in English.
• C. The sound of an r-controlled vowel is always the same as the base vowel plus 'r' in every word.
• D. R-controlled vowels occur only in the word 'bird'.

Answer: (A)