Consider a hypothetical processor with an instruction of type LW R1, 20(R2), which during execution reads a 32-bit word from memory and stores it in a 32-bit register R1. The effective address of the memory location is obtained by the addition of a constant 20 and the contents of register R2. Which of the following best reflects the addressing mode implemented by this instruction for the operand in memory?

In the instruction LW R1, 20(R2):

• The effective address (EA) is computed as $\text{EA} = \text{offset} + [\text{R2}] = 20 + [\text{R2}]$.

• Here, a base register (or index register) content is added to a constant displacement (or index/offset) to compute the target memory address.

• This addressing mode is known as Base Indexed Addressing (or Displacement / Base-Register Addressing).

Therefore, option (D) is the correct choice.