c. Sign extension.
When a signed value is loaded into a register, it needs to be properly sign-extended to ensure that the correct signed value is represented. The sign of a signed value is indicated by the most significant bit, with a value of 0 indicating a positive value and a value of 1 indicating a negative value. If the most significant bit of a signed value is a 1, then the value is negative. Sign extension involves copying the most significant bit of the signed value into all of the higher-order bits of the register to ensure that the correct sign of the value is maintained. This ensures that the value is properly represented as a signed value, and that arithmetic and logical operations on the value will yield the expected results.