language development is initially triggered

Question

a.socially
b.pschologically
c.biologically
d.by parental contact

my answer is d

Answer 1

I agree.

Answer 2

guess that answer is wrong

Answer 3

slthough most children appear to learn their language with ease,this ease conceals a phychological process of amazing complexity.for some time ,psychologists have speculated on how language learning actually occurs.

that's what the text say ,can someone please help