你知道最近的邮局在哪里吗？

Do you know ___where the nearest post office is?

这条漂亮的项链是从哪里来的？

___Where did you get this lovely necklace from?

你知道钥匙放在哪里吗？

Do you know ___where I put the keys?

这是项目中最关键的一步，我们需要在此做出重要选择。

This is the stage ___where we need to make crucial choices for the project.