A the difference between active vocabulary and receptive vocabulary must be disregarded as a factor to estimate how many words a person knows.
B undergraduate students acquire vocabulary related to word families after enrolling at universities.
C the similarity of some word families prevents students from counting the number of words they really know.
D both native speakers and second language learners have a larger passive vocabulary than an active vocabulary.
E studies are certain that the average English speaker knows about 1,000 words by the time she or he starts Kindergarten.