Which of the following shift instructions is used to retain the sign bit…

Arithmetic Shift Right (ASR) preserves the sign bit by replicating it during right shifts. This ensures signed binary numbers maintain their correct value and sign after shifting operations.

Note for more Understanding

To solve this, the Arithmetic Shift Right instruction duplicates the sign bit during the shift.

Example 1 (Positive Number):

Let's take +8 in an 8-bit signed system: 00001000.

Performing an ASR by 1 position moves everything right, and copies the sign bit (0) into the vacancy:

Result:  0000100        (+4)

Example 2 (Negative Number):

Let's take -8 in an 8-bit signed system: 11111000.

Performing an ASR by 1 position moves everything right. To preserve the negative status, the sign bit (1) is copied into the vacancy:

Result:  11111100   (-4)

Because the sign bit is replicated rather than replaced, the arithmetic integrity and polarity of the signed number are preserved perfectly throughout the operation.