Sometimes something is so true yet someone isn't sure or doubts it. By replying with a question that can have only one answer, it confirms the first statement as obvious. Here are some examples.
Do one legged ducks swim in circles?
Does Dolly Parton sleep on her back?
Do whales have blubber?
Is the sky blue?
Can fish swim?
Do chickens lay eggs?
Is water wet?
You can easily make up your own. Then there is the opposite, saying something cannot be true. They are not so common:
Do chickens have lips.
Do pigs fly?
If you know any, add a comment and I may add it to the list. Keep it seemly.