Toddler Arielle Sees a Baby Being Tickled by a Boy

Toddler Arielle sees a baby being tickled by a boy and hears her mother say, "The boy is tickling the baby." Arielle has never heard anyone use the word "tickling." Arielle figures out that "tickling" is what the boy is doing to the baby, not what the baby is doing (laughing and waving her arms in delight) , through: ______.

A) syntactic bootstrapping.
B) intersubjectivity.
C) fast mapping.
D) attending to the linguistic category of the novel word.