此句是否省略了that

熱心網友

Perhaps the most difficult challenge is that how to survive without friends. 是,賓語從句!

熱心網友

是表語從句，Perhaps the most difficult challenge是主句，is how to survive without friends是系動詞加上表語從句，that引導表語從句可以省。

熱心網友

這是同位語從句。

熱心網友

Perhaps the most difficult challenge is how to survive without friends.這里的how to survive without friends引導表語從句.不需要that

熱心網友

沒有省略how to survive without friends在be動詞后邊，是表語從句。已經有how引導，不必再用that引導

熱心網友

不是.that引導的是陳述句.