Final answer:
The fields on the Account table that allow Contacts to self-register on the Portal are the Username and Password fields.
Step-by-step explanation:
The fields on the Account table that allow Contacts to self-register on the Portal are the Username and Password fields. The Username field is where the Contact enters a unique username that they will use to login to the Portal. The Password field is where the Contact sets a secure password for their account. Once a Contact fills in the required information and submits the registration form with a valid Username and Password, they will be able to access the Portal using these credentials.