What is the most logical next event?

How to convince your parents not to sell your pet
Have a strong argument for keeping your pet.
If you want your parents to listen to you, you will have to show that you put thought into what you are saying. You should be able to cite specific reasons as to why keeping the pet is a good idea (e.g. teaching you responsibility).
It will also help if you can find sources online or in print that back up your claims. Even if you think the reasons are common sense, show them that you really cared enough to do some research about it.