In a Cisco router, which set of memories correctly lists the main memory types typically used (for example, to store IOS image, configuration, and runtime data)?

Introduction / Context:
Cisco routers and similar network devices use several different types of memory, each with a specific purpose. Understanding these memory types helps you know where the IOS image resides, where configuration files are stored, and how runtime data is handled. This question asks you to identify the standard set of memories commonly discussed in Cisco certification courses.

Given Data / Assumptions:

The context is a Cisco router or similar enterprise router device.
We are interested in the main onboard memories used for system image, configuration, and operation.
Standard Cisco material typically refers to four major memory types.

Concept / Approach:
Cisco routers normally include RAM, ROM, NVRAM, and Flash memory. RAM (Random Access Memory) holds the running configuration and routing tables during operation. ROM (Read Only Memory) contains bootstrap code and basic diagnostics. NVRAM (Non Volatile RAM) stores the startup configuration that is loaded during boot. Flash memory is used to store the IOS image and sometimes additional files. These four types together support booting, configuration, and runtime functions. Media such as DVD, CDs, and tapes are not integral built in memories of typical routers and are not used in the same way.

Step-by-Step Solution:
Step 1: Recall from Cisco study materials the names and roles of memory types in a router.Step 2: Identify that RAM, ROM, NVRAM, and Flash are the core memories mentioned.Step 3: Compare each option and select the one that lists exactly these four memory types.Step 4: Confirm that the other options include storage media not typically described as router memories.

Verification / Alternative check:
To verify, you can map each memory type to its role. RAM holds the running configuration and dynamic data. NVRAM holds the startup configuration. Flash stores one or more IOS images. ROM contains the bootstrap program and simple diagnostic software. When you see all four together in one answer choice, you can be confident that it is the correct list.

Why Other Options Are Wrong:
Option B is wrong because DVD and SD card are removable or external storage media, not the standard, built in memories always discussed in router architecture basics.
Option C is wrong because magnetic tape and CD are not typical parts of router memory architecture; they are external media used in other contexts.
Option D is wrong because a Cisco router does not rely on only a single type of memory like EEPROM for all purposes; there are distinct memory types for different functions.

Common Pitfalls:
Some students associate any storage medium with router memory without distinguishing internal architectural components from external media. Another pitfall is to remember only RAM and Flash and forget about ROM and NVRAM. For exam success, always keep the list of four main memory types together and know what each one stores and when it is used in the boot and configuration process.

Final Answer:
RAM, ROM, NVRAM, and Flash