By the age of ______ and a half years, children’s vocabulary is

By the age of ______ and a half years, children’s vocabulary is expanding rapidly and they are actually initiating more talks.
A、one
B、two
C、three
D、four
【正确答案】：B
【题目解析】：By the age of two and a half years, children’s vocabulary is expanding rapidly and they are actually initiating more talks.