This is the reason why I came late.

This is why she is still angry with me.

This is why he got angry with you.

This is the reason why I came here.

Why should you think so?

Why on earth did you do that?

Why don't we share a room?

"Why?" asked the daughter, a trifle irritated.

Why is it the mass media didn't report this?

Why do you love me?