Tom: Where is my backpack?
我的背包在哪里？

Marry: I don't know. Where did you leave it?
我不知道。你把它放在哪里了？

Tom: I just put it on the chair a while ago, but now it's gone.
一段时间之前我把它放在椅子上了，但是现在不见了。

Marry: Are you sure?
你确定吗？

Tom: Of course, I'm sure. I bet someone stole it.
当然，我确定。我敢可能它被人偷走了。

Marry: Well, you should've kept an eye on it.
额，你本来应该照看好它的。