Final answer:
The stage of the access control process taking place when Toby is asked to provide a password after entering his username is Authentication.
Step-by-step explanation:
When Toby provides his username at the prompt and is then asked to provide a password, the stage of the access control process that is taking place at that moment is Authentication. Identification has already been done when he entered his username, confirming who he claims to be. Authentication is the process where the system verifies whether Toby is indeed the person that corresponds to the username provided, typically by matching the provided password to one on record. After successful authentication, Toby would eventually go through Authorization, which determines what resources he can access or what operations he can perform within the system.