Here's how I see it. Only the last hash parameter *can* omit the braces. That's Ruby syntax. If you want the `presence` and `length` values to go in two different parameters, you have to put braces around `presence: true`. Then you can put braces around `length: { within: 1..10 }`, or leave them out. It won't change the meaning. It's just a style issue and that's what we're checking.