The induction system for a normally-aspirated engine comprises three main sectors. Which option lists them correctly?

• A. An air intake (scoop) and duct to direct ambient air to the carburetor; The carburetor; The inlet manifold between carburetor/throttle unit.
• B. The air intake and duct; The carburetor; The exhaust manifold.
• C. The air intake; The throttle valve; The fuel pump.
• D. The air intake and duct; The carburetor; The inlet manifold between carburetor/throttle unit.

Answer: (A)

The three main sectors of a normally aspirated engine’s induction system are the path that brings in ambient air, the device that meters fuel and blends it with that air, and the manifold that distributes the resulting mixture to the cylinders. The air intake and its duct guide outside air to the carburetor; the carburetor performs fuel metering and air–fuel mixing; and the inlet manifold sits between the carburetor and the throttle/cylinder ports to deliver the mixture to each cylinder. Components outside this path, like the exhaust manifold, aren’t part of the induction system, and the fuel pump belongs to the fuel system rather than induction. The throttle valve is internal to the carburetor, so treating it as a separate sector isn’t correct. Therefore, listing the air intake and duct, the carburetor, and the inlet manifold between the carburetor and throttle unit accurately describes the three main sectors.