As an acceptance tester you are analyzing the following user story for a computer web-based...

As an acceptance tester you are analyzing the following user story for a computer web-based mass multiplayer role-playing game:

As an unregistered player

I want to be able to register myself by defining my e-mail, login and password in a registration form so that I become a registered player

Consider the following propositions of the acceptance criteria:

i.a registration form is displayed on the screen.

ii.the form is written in the Groovy language; the cursor is initially set on the ‘login’ field; after pushing the TAB button the cursor switches to ‘password’, ‘repeat password’, ‘mail’, and ‘repeat mail’ forms.

iii.I cannot register myself if the login I choose is used by another player.

iv.after successful registration process I am informed about it by an e-mail.

Which of the above statements would you consider as well-written acceptance criteria?