Direct Addressing:

In direct addressing, the memory address is directly given in the instruction.

So, STA, FFFFA is direct addressing.

a → III

Indirect Addressing:

In indirect addressing, the memory address is given indirectly through a register pair.

In MOV A, M, M represents the memory location pointed by HL register pair.

b → IV

Register Addressing:

In register addressing, operands are registers.

MOV A, B uses registers A and B.

c → II

Immediate Addressing:

In immediate addressing, data is directly given in the instruction.

MVI A, FFH means FFH is directly loaded into A.

d → I

Correct matching:

a-III, b-IV, c-II, d-I