Jack didn't know where he could find his mother变为简单句

Jack didn't know where he could find his mother变为简单句
Jack didn't know where he could find his mother变为简单句

Jack didn't know where he could find his mother变为简单句
Jack didn't know where to find his mother.

where he could ----------where to

Jack can't find (out) his mother
其实原句konw 和 where 之间省略了that 。这是一个定语从句～
^_^个人观点，仅供参考～

应该是 Jack didn't find his mother anywhere。