In a two-stroke cycle, opposed-piston, diesel engine, one crankshaft operates several crank angles in advance of the other crankshaft to __________.

Correct Answer: Option A — allow the exhaust ports to open and close before the inlet ports close

Advanced timing on the upper crankshaft of an opposed-piston two-stroke marine diesel engine allows the exhaust ports to open before the intake ports and close after them. This phase lead optimizes cylinder scavenging efficiency, power output, and thermal performance.