【题目】It is so good a habit to instruct children to lay things they belong when they are yong.
A.to which
B.that
C.in which
D.where

【答案】D
【解析】考查地点状语从句。句意：在孩子小的时候教育他们把东西放在应该放的地方是个好习惯。本处where they belong作为lay things的地点状语从句。结合语境，所以答案是D。