The correct answer is A) Cross-flow scavenging. In a slow-speed two-stroke cycle diesel engine with scavenging air ports and exhaust ports located on opposite sides of the cylinder wall, the scavenging flow-pattern utilized is cross-flow scavenging. This is because the fresh air/fuel mixture enters the cylinder through the scavenging air ports on one side and flows across the cylinder to exit through the exhaust ports on the opposite side, creating a cross-flow pattern. The other options are incorrect because B) Uniflow scavenging involves the fresh charge and exhaust flowing in the same direction, C) Return-flow scavenging uses a loop-shaped flow pattern, and D) Loop scavenging is a different type of flow pattern not applicable to this engine configuration.