According to the data, which age corresponds to 90% language acquisition?

• A. 2 years
• B. 3 years
• C. 5 years
• D. 4 years

Answer: (D)

Language development progresses rapidly in early childhood, with most features of speech and grammar reaching high levels of mastery by a certain age. The data show that around four years old, children typically have about 90% of language acquisition in place—their pronunciation, grammar, and vocabulary are largely developed, allowing for clear conversation and more complex sentences, even though some advanced nuances may still be developing. Earlier ages show smaller percentages of mastery, while by about five years old language is usually near full maturity. So, the age that corresponds to roughly 90% language acquisition is around four years.