How many copies of the alert log are stored in the directory specified by the initialization parameter DIAGNOSTIC_DEST?

Answer: D

Explanation: The alert log is stored in XML format in the alert subdirectory and in text format in the trace subdirectory. The alert log as well as all other diagnostic information is maintained per instance (for each instance). A is incorrect because an alert log exists for each database instance, which is the case in a RAC environment. B is incorrect because the alert log is stored in both XML and text formats. C is incorrect because two copies of the alert log exist per instance, not per database. E is incorrect because the alert log is not stored in an incident directory.