1.There are mainly three stages ---- every child will experi

1.There are mainly three stages ____ every child will experience,but the age ______ they reach each stage is different.
第二个空填 at which我清楚.问题是第一个空：stage作先行词定语从句不是应该由where来引导吗?为什么用which?
2.guidance是不可数名词吗?
3.as well as 后面的谓语动词是用单数形式吗?
4.For some children,there seems no such _____ thing as "free" time of their own,which has now been _____ great concern of some educational experts.
第一个空为什么不用填冠词?