What is the main feature of container ships designed for unitized cargo?

The main feature of container ships designed for unitized cargo is the built-in cell guides for securing cargo. These cell guides are critical in facilitating the efficient loading, unloading, and securing of containers on board. They allow containers to be stacked securely, minimizing the risk of shifting during transit and ensuring the stability of the ship. This design optimizes space and enhances safety while accommodating standardized shipping containers, which is essential in modern supply chain logistics.

Other options do not capture the primary design aspect of container ships focusing on unitized cargo. While multiple loading decks may enhance access and efficiency, they are not specific to container ships. Likewise, while cranes are commonly used in port operations with container ships, they do not define the ship's design itself. High-speed propulsion systems are important for reducing transit times but are not a distinctive feature of container ships regarding how they handle unitized cargo.