The email address you've got registerd with Garavatar, UKA, must be the same one that The Answerbank has registered for you. (It's the only way that AB's server can find your avatar on Gravatar). To see which one it is, simply click on 'View your profile' (at the top right of this page) and then on 'Edit my profile'.
You don't need to be able to get into that email account to change your avatar unless you've lost/forgotten your password for Gravatar/WordPress.
So, as long as you know that password, you simply need to go here and sign in:
http://en.gravatar.com/
If you've forgotten your Gravatar/WordPress password, but you can still access the relevant email account, use the 'Sign in' button and then get a pasword link sent to that account.
If you've forgotten your Gravatar/WordPress password AND you can't get into the relevant account either, create a NEW email addres somewhere (e.g. here:
https://www.gmx.co.uk ). Next register for a NEW Gravatar account, using that email address, and upload your new avatar. Lastly, go back to 'Edit My Profile' on AB, change your email address in both fields, enter your AB password (NOT your Gravatar one) in the box at the bottom of the page and hit 'Submit'.