Celia has noticed that her 7-month-old daughter has recently begun to raise and lower the pitch of her voice when she babbles so she sometimes sounds as if she is asking questions. Celia's daughter has added __________ to her babbling. a.cooingc.vowel sounds b.repetitiond.intonation

# Brief Explanations: <br />Celia's daughter is evolving in her communication skills by adding variation in pitch, often serving to indicate questions, emotional intent, or other linguistic nuances. This variation in pitch, also known as vocal inflection, is referred to as 'intonation' in linguistic terms. It is not cooing, which is an early stage of baby talk that often consists of vowel sounds. Neither is it solely vowel sounds or repetition of sounds which are also elements of earlier speech development stages.<br /><br /># Answer: <br />d. intonation