Why Are Overextensions More Common in Toddlers' Production of Words

Why are overextensions more common in toddlers' production of words than in their comprehension?

A) They are generally unable to combine words into grammatically correct sentences.
B) They rely on a limited vocabulary when expressing themselves.
C) They often fail to attend when parents provide proper labels for objects or events.
D) They have not learned to consistently identify objects or events they encounter.