Solution

The correct answer is : option 1

Key Points

• In basic computer architecture, a memory reference instruction is typically identified by the first bit being 1.
• If the first bit is 0, the instruction is either a register-reference or an input/output instruction, not a memory reference instruction.

Conclusion:

• Only Option B has 1st bit = 0, so it does not represent a memory reference instruction.
• Option C is slightly tricky due to opcode 111, but since 1st bit is 1, it is still considered memory reference.
• The best possible answer from the given options is: Option 1) B & C only, even though technically only B is incorrect.

✅ Final Answer: Option 1) B & C only