【题目】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
在线课程【答案】A
【解析】考查定语从句。as 引导的定语从句位置比较灵活，可以置于句首，句中或句末。as为代词，代指“语言学习在出生后的第一年就已经开始发生”这件事。which引导的定语从句只能放在句末。