AnINFOmessage is written only when the configured logging threshold permits INFO-level events and INFO output is enabled for the relevant custom log destination. Setting the root level toDEBUGpermits DEBUG and all higher-severity messages, including INFO, WARN, ERROR, and FATAL. Enabling theInfolog-file option ensures that INFO messages are written to the applicable log file.
Salesforce ' s logging documentation explains that custom DEBUG and INFO logging can be enabled through Business Manager ' s custom log configuration and that the selected log levels control which messages are persisted. The logger ' s threshold behavior also means that a DEBUG root threshold includes INFO-level events because INFO has a higher severity.
The "logging global preference" described in options B and C is not the relevant mechanism for solving this custom logger configuration issue. Either of those options would also omit one of the two necessary controls described in option A.
Thus the developer should configure both the permitted log-level threshold and the INFO file output, then execute the code again and inspect the generated custom log through Log Center or WebDAV.
Study Guide reference:Application Development - custom logging, log levels, Business Manager log configuration, and WebDAV diagnostics.