Question

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

Answer

A

【解析】空白处所在句为非限制性定语从句，故B、D两项可排除。由句意知空格处的关系词指代a lot of language learning is happening in the first year of life这个句子。指代某个句子时，as引导的非限制性定语从句可后指或前指，而which引导的从句只能前指。这里是后指。句意：正如被发现的那样，大量的语言学习是在人生的第一年发生的，所以父母应当在那个时期和孩子多说话。