A Cow Rolls Again

A Cow Rolls Again

How did the cow eat grass?
Without knowing where it was going.
Why did the cow moo?
She was on a roof.
How did the cow eat grass?
Her chewing is slow.
Why did the cow moo?
She ate her tooth.
Why is there grass on the roof?
A sloped ridge hides the building.
What makes three loud thumping sounds?
A goose, the roof and a tooth.