the door locks中的door怎么不加's

from door to door怎样加s S(),the door opened 文中一句话：She's next door,请问door前面不需要加the吗? look,the door is open,为什么open不加ing? it's( ) the door.这个空怎么填,要介词 Listen!Who`s( )on the door?怎么填? door what's behind the door 语法结构 where's the key?it's____the door There’s somebody()behind the door. What's under the door?改错句 There's someone ___ the door.