1.The subi (subtract immediate) instruction does not exist as an instruction in MIPS.

subi $t0, $t1, 8 # Reg[$t0] = Reg[$t1] - 8

Which of the following is the reason why? (Select 1)

A: All arithmetic instructions must be R-type.

B: The immediate field must be a signed value.

C: Pseudo instructions are useless.

D: The same operation can be performed with the addi instruction because the immediate field is a 2's complement value

2.

Which of the following correctly describes an opcode?

(Select all that apply)

A. The field is 5 bits of the instruction format.

B. The opcode field is the most significant bits of each instruction.

C. The opcode is unique for every instruction.