“where”是疑问副词,通常用于构成特殊疑问句或宾语从句,例如:
1. 特殊疑问句:Where are you from?(你来自哪里?)
2. 宾语从句:I don't know where we should go.(我不知道我们应该去哪里。)
引导的是一个定语从句,where表示模糊地点。即 they are both born in a single child family in policy. 用that肯定是不对的,that 可做关系副词,但仅指替表时间的词。 还有, a sudden in crease in population 这里应该是你打错了 ,正确的应是 a sudden increase in population . 有不懂再问吧。