What is the size of an amphibious transport dock?

The size of an amphibious transport dock can vary among different classes and types, but the answer indicating 680 feet long with a beam of 105 feet is representative of a common size for these vessels, especially for the San Antonio-class (LPD 17) amphibious transport docks used by the U.S. Navy. These ships are designed to transport and land Marines, their equipment, and supplies via embarked landing craft and helicopters. The dimensions help to ensure that the ship is capable of carrying a significant load while maintaining operational functionality in various environments.

In this context, the other options may reflect dimensions that do not align with the specifications of the most widely recognized amphibious transport docks in service today, which may either be too long, too short, or have a beam measurement that is not typical for such vessels. The specific measurements of 680 feet in length and 105 feet in beam provide an appropriate balance between capacity and navigational needs, making option B the most accurate answer for typical amphibious transport dock dimensions.