What characteristic differentiates the High Capacity (*E-type*) coupler?

Answer: B — It has rounded corners

The characteristic that differentiates the High Capacity E-type coupler is that it has rounded corners. This design feature is significant because the rounded corners help to reduce stress concentration points, which can lead to increased durability and reduce the risk of failure under load. The design also facilitates smoother coupling and uncoupling processes, which is essential in the operation of trains, particularly under heavy loads. In contrast, other characteristics could be associated with different coupler types. For instance, size may vary among coupler types but is not a definitive characteristic of the High Capacity E-type coupler. Being electrically activated is more typical of newer technology couplers rather than being a defining trait of the E-type. The locking mechanism is also a common feature in many coupler designs, which means it doesn't specifically differentiate the High Capacity E-type from other couplers.