Final answer:
The true statement about field-level security is that it is enforced in the Web Services API, which applies to programmatic access of a system's data.
Step-by-step explanation:
The statement that is TRUE about field-level security is that it is enforced in the Web Services API. Field-level security settings allow administrators to restrict users' access to view and edit specific fields. It is an important concept within systems like Salesforce, where field-level security is a feature that helps in maintaining data privacy and compliance by controlling the visibility and editability of fields.
Field-level security is indeed specified on the profile of the user in question; however, it cannot control visibility and editability of fields at the record level—that is managed by other features such as record types and sharing rules. Also, it does not determine the values displayed in a visible picklist field; those are typically determined by the field's configuration or by record type settings.
The enforcement of field-level security in Web Services API ensures that the restrictions imposed by administrators apply not only within the user interface but also when the system is accessed programmatically through APIs.