Logger.getLogger( ' contact ' )creates or retrieves a logger associated with thecontactcategory. Calling.debug() on that logger writes the message at DEBUG severity, subject to the configured category and log-target rules.
B2C Commerce custom logging uses hierarchical category names patterned after log4j. Categories can be activated at particular severity levels inAdministration > Operations > Custom Log Settings. Salesforce explains that child categories inherit applicable settings from their parent categories unless they have more specific configuration.
Option B uses the generic staticLogger.debug()call and does not explicitly associate the statement with the required customcontactcategory. Option C refers to a nonexistentcustomLogger()API.
The category-specific approach is operationally superior when troubleshooting a third-party integration because administrators can selectively enable DEBUG logging forcontactwithout enabling extensive debugging across unrelated application code. Once the issue is diagnosed, that category ' s verbosity can be reduced again.
Study Guide reference:Application Development -dw.system.Logger, custom categories, DEBUG logging, Service Framework diagnostics, and hierarchical logging configuration.