Question

read the text.
language acquisition
almost all humans acquire at least one language before the age of five.
although people gain vocabulary throughout their lifetimes, even young
children are able to understand and produce complex sentences with
complicated meanings. how do children accomplish this remarkable feat in
such a short amount of time? do adults learn language differently from
children? linguistic researchers have long debated the answers to these
questions, but most agree that both nature and nurture are involved in
language acquisition. they disagree, however, about how much linguistic
knowledge children have from birth—and thus whether genetics or
experience is more important in language acquisition.
what is the main focus of the text?
the dominance of nurture over nature in language acquisition
the best methods for children and adults to acquire language
the role of biological and environmental factors in language acquisition
how language acquisition is driven by universal grammar

Explanation:

The text mentions that both nature (biological, related to genetics) and nurture (environmental, related to experience) are involved in language acquisition, and the debate is about their relative importance. It doesn't say nurture dominates (so first option is wrong). There's no discussion of best methods (second option wrong). Universal grammar isn't mentioned (fourth option wrong).

Answer:

the role of biological and environmental factors in language acquisition