Concept:Door-to-door service means a transport mode can carry people or goods directly from the starting point to the final destination without transferring to another vehicle.
Explanation:Rail transport operates on fixed tracks and stops at stations.
Ocean transport uses ports and sea routes, while air transport requires airports and runways.
These modes cannot reach every individual home or business directly.
Road transport uses an extensive network of roads that connect homes, farms, factories, and markets.
Trucks, buses, and cars can therefore begin and end their journey at the exact desired location.
Hence, road transport offers the easiest and most flexible door-to-door service.
Answer:A. road transport