[Q]: Air leaked out of the beach ball.

cause: 
[A]: There was a hole in it.
[Q]: I rubbed sandpaper on the wood.

effect: 
[A]: The wood became smooth.
[Q]: The girl politely declined the hamburger.

cause: 
[A]: She was a vegetarian.
[Q]: I drank a cup of coffee.

effect: 
[A]:
My yawning ceased.