She lost the key to the door.

她把房间的钥匙丢了。

This is not the key to the door.

这不是那扇门的钥匙。

I lost the key to the door.

我把门钥匙丢了。

I have mislaid my key to the door.

我不知道把门钥匙放到哪里了。

It's a key to the door.

这是那扇门的钥匙。