When Young Children Overregularize and Produce Forms Such as Tooths

When young children overregularize and produce forms such as tooths, satted, or goed, as well as correct forms (e.g., walked, played, and cars) , what are they demonstrating?

A) that they do not yet understand grammatical transformation rules
B) that they have learned a rule for producing word endings, but they have failed to retrieve the correct form of an irregular word
C) that they are imitating the "baby talk" of other young children
D) that their parents must be providing poor language models for them or failing to correct the child's mistakes