To solve this question, the user needs to understand the MOV and CMP assembly instructions.

MOV is a transfer instruction that moves data from a source operand to a destination operand. In this case, the source operand is the immediate value 456h, and the destination operand is the AX register. This instruction copies the value 456h into the AX register.

CMP is a comparison instruction that compares two operands and sets the appropriate flags in the flags register based on the result of the comparison. In this case, the operands are the AX register and the immediate value 456h. This instruction subtracts the value of the immediate operand from the value of the AX register and sets the appropriate flags based on the result.

Now, let's go through each option and explain why it is right or wrong:

A. 456h: This option is correct. The MOV instruction moves the value 456h into the AX register, so the AX register contains the value 456h. The CMP instruction does not modify the value of the AX register.

B. Zero: This option is incorrect. The MOV instruction moves the value 456h into the AX register, so the AX register contains the value 456h. The CMP instruction does not modify the value of the AX register.

C. 1: This option is incorrect. The CMP instruction does not affect the value of the AX register, so the value of the AX register remains 456h.

D. Unknown: This option is incorrect. The MOV instruction moves the value 456h into the AX register, so the value of the AX register is known to be 456h. The CMP instruction does not modify the value of the AX register.

Therefore, the answer is: A. 456h