What is the purpose of voter registration?

A big reason is taxes. Once you register to vote, your registration will be used for tax lists, voter lists, and in health care systems. Another reason it's important to register is so that you will recieve your card that says when and where to vote. Since voting is the right of a democracy, voter registration helps voters check in and make sure they're eligible, anyways. Hope this helps!

Im pretty sure the answer is d.) is more densely populated.