The correct answer is: A. /var/log
The /var/log directory is the standard location for system and mail logs in Red Hat Linux. This directory contains a number of subdirectories, each of which contains logs for a different type of system activity. For example, the /var/log/auth.log file contains logs of all authentication attempts, while the /var/log/kern.log file contains logs of all kernel messages.
The /etc/log directory is a configuration directory that contains files that control the logging system. These files specify the location of the log files, the types of events that should be logged, and the format of the log entries.
The /mail directory is the standard location for mail spools in Red Hat Linux. A mail spool is a directory that contains incoming and outgoing mail messages.
Therefore, the correct answer is A. /var/log.