单元检测(六)一、单项填空(共15小题;每小题1分,满分15分)请从A、B、C、D四个选项中,选出可以填入空白处的最佳选项。1.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.this2.There are over 58,000 rocky objects in ________ space,about 900 o