问题补充：
Some children don’t know for their parents.
A. what can they care
B. how can they care
C. what to care
D. how to care
答案：
A. what can they care
B. how can they care
C. what to care
(答案→)D. how to care
解析：句意：一些孩子不知怎样关心他们的父母。宾语从句用陈述句语序，故排除AC。怎样照顾父母，故选D。
