Children of bilingual parents who teach them both languages in infancy and early childhood

A) generally take five to seven years to attain speaking and writing skills on par with those of monolingual agemates.
B) attain language milestones in both languages far later than monolingual agemates.
C) have a much smaller and less sophisticated vocabulary than monolingual children.
D) separate the language systems early on and attain early language milestones according to a typical timetable.

D