Which of the Following Is the Best Example of a Child's

Which of the following is the best example of a child's first word,according to linguists?

A) Dylan repeats the consonant and vowel syllable "dah" over and over again with rhythmic intonation.
B) Rosario says "goggie" when she is referring to the family dog or her sister.
C) Indira points to her blanket, opens and closes her hand, and grunts repeatedly.
D) Beth says "ba" and points when she wants her bottle.