Stefan Is Babysitting His Young Niece, Avery, for the First

Multiple Choice

Stefan is babysitting his young niece, Avery, for the first time. Stefan has not seen Avery since the beginning of the semester, and is surprised to find that Avery is speaking much more than she did the last time. Stefan has just been through a lecture on language development, so he thinks this visit will be especially interesting.
-Avery knows the difference between a cat and a dog,can express her own ideas,and is learning grammar,but she cannot read or write.Which of the properties of language has she not mastered yet

A) symbolic
B) semantic
C) infinite generativity
D) structure