AMC users have access to all AMC instances in an account by default.

The correct answer is False because AMC users do not automatically have access to all AMC instances within an account by default. Access to AMC instances is controlled by permissions and roles that are set by administrators, and each user is typically granted access to specific instances based on their role and the requirements of their work. This helps ensure data security and appropriate access levels, as different users may need access to different sets of data depending on their responsibilities. Therefore, it is not true that all AMC users have access to every instance within an account without explicit permissions being granted.