A lot of language learning ,_______has b
题型：选择题
问题：
A lot of language learning ,_______has been discovered, is happening in the first year of life, so parents should talk much to their children during that period .
A．as
B．it
C．which
D．this
A lot of language learning ,_______has been discovered, is happening in the first year of life, so parents should talk much to their children during that period .
A．as
B．it
C．which
D．this