It is normally assumed that, by the age of ______, with an opera

It is normally assumed that, by the age of ______, with an operating vocabulary of more than 2000 words, children have completed the greater part of the language acquisition process.
A、one
B、two
C、three
D、five
【正确答案】:D
【题目解析】:It is normally assumed that, by the age of five, with an operating vocabulary of more than 2000 words, children have completed the greater part of the language acquisition process.