(I) Many linguists are convinced that children do
not simply acquire language by imitation, but stating
this does not diminish the crucial importance of
exposure to linguistic input from adults in acquiring a
language. (II) Linguists who claim that language
acquisition is not a mere imitation of adult speech think
that children know more about language than what is
contained in linguistic input they are exposed to.
(III) Acquisition definitely requires interaction with
speakers of the language being acquired, because
when adults talk to children, they directly or indirectly
offer extensive information about their language.
(IV) As witness to the necessity of adult input, there is
the case of Genie, a child who was deprived of linguistic
input in the first 13 years of her life beacuse her parents
seldom spoke to her. (V) When she was discovered,
Genie’s capacity for language acquisition had become
impaired.

Which of the sentences in the given paragraph is
irrelevant, violating its unity and coherence?