How do you know he is depressed?

How do you know he is depressed? how old is he?do you know?2并1 do you know how old_______ ___ Then how do you know he is happy? 为什么是Do you know how old he is而不是he is? do you know how old she is Ten how do you know he is happy?翻译过来是什么 Then how do you know he is happy（翻译中文） Do you know who is he? How do you know? do you know how() how do you know Do you know Who he is?能不能是Who do you know he is