During the valve overlap period, the exhaust pressure of a turbocharged, four- stroke/cycle diesel engine must be less than the intake manifold pressure to ensure __________.

Correct Answer: Option A — effective cylinder scavenging and cooling

During valve overlap, intake manifold pressure must exceed exhaust pressure to force scavenging air through the combustion chamber. This pressure differential clears burnt gases, cools exhaust valves, and prevents backflow into the intake manifold.