问题补充：
Children should be instructed to put thingsthey belong in their early childhood.
A. where
B. in which
C. to which
D. what
答案：
A. where
B. in which
C. to which
D. what
解析：选A。考查状语从句。句意: 在童年时代早期就应该指导孩子们把东西放在它们所属的地方。四个选项只有where可以引导地点状语从句。
【误区警示】本题易误选C项, 以为是“介词+关系代词”引导的定语从句, 但实际上本句中不存在定语从句的先行词。
