In a two-stroke diesel engine, uniflow scavenging is considered the most efficient scavenging method. What arrangement defines uniflow scavenging?

1. A. Intake ports and exhaust ports are both located in the cylinder liner at opposing positions near bottom dead center
2. ✓ Intake ports are located low in the liner and exhaust valves are in the cylinder head, so the fresh charge moves in one directionCorrect
3. C. A Roots-type blower forces exhaust gas back through the intake ports to cool the combustion chamber
4. D. Intake and exhaust both occur through poppet valves in the head, timed by the camshaft