To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) The source of commonly used configuration commands - This option is incorrect. NVRAM, or Non-Volatile Random Access Memory, is not directly related to the source of commonly used configuration commands.
Option B) The primary source of the Cisco IOS - This option is incorrect. NVRAM is not the primary source of the Cisco IOS. The Cisco IOS is typically stored in the router's flash memory.
Option C) A location to run the active configuration from - This option is incorrect. NVRAM is not used to run the active configuration. The active configuration is stored in the router's RAM.
Option D) A location to run the power on diagnostics from - This option is incorrect. NVRAM is not used to run power on diagnostics. Power on diagnostics are typically run from the router's ROM.
Option E) A location to store a backup copy of the router configuration file - This option is correct. NVRAM is a type of memory in a router that retains its data even when the power is turned off. It is commonly used to store a backup copy of the router's configuration file.
Therefore, the correct answer is E) A location to store a backup copy of the router configuration file.