An "Unknown Error Code" Is Appearing on an ESXi Host

An "unknown error code" is appearing on an ESXi host during authentication. An engineer checks the authentication logs but is unable to identify the issue. Analysis of the vCenter agent logs shows no connectivity errors. What is the next log file the engineer should check to continue troubleshooting this error?

A) /var/log/syslog.log
B) /var/log/vmksummary.log
C) var/log/shell.log
D) var/log/general/log