(Why/How/What) on Earth (question)?

Starting a question with "Why on Earth...?" or "How on Earth...?" shows that you feel totally surprised by the thing that you're asking about. For example:

How on Earth did you get up there?

This is something you can ask someone who's standing on the roof of a house unexpectedly.

What on Earth are you talking about?

Ask this when someone says something really confusing.

This phrase appears in these lessons: