Q.Which of the following performs arithmetic and logical operations in the CPU?
(A) Control Unit
(B) Registers
(C) Arithmetic and Logic Unit (ALU)
(D) Address bus

The clue is in the name — the unit that does calculations and comparisons is named after exactly those operations.

The control unit only directs and coordinates; registers only hold data temporarily; and the address bus only carries memory locations. The actual computation happens in the ALU.

Section b describes the three parts of the CPU. The arithmetic and logic unit (ALU) is the part that does the actual work of computing — it performs arithmetic operations (addition, subtraction, multiplication, division) and logical operations (comparisons such as equal to, greater than, less than, and true/false decisions). All the real calculation in a computer happens here.

The distractors do other jobs: the control unit (A) fetches, decodes, and directs instructions but does not itself calculate; registers (B) are tiny fast stores that merely hold the data being worked on; and the address bus (D) is not part of the CPU's processing at all — it is a pathway that carries memory addresses. Only the ALU performs arithmetic and logic.

Do not confuse the ALU with the control unit. The ALU does the calculations; the control unit only directs the work. Remembering that "Arithmetic and Logic" is literally in the ALU's name prevents this mix-up.