Which of the following is a stern chock used when towing another ship?

The towing chock is specifically designed for use in towing applications, making it the appropriate choice for this question. A towing chock provides a secure point for the towing line to interact with the ship's structure, ensuring that the forces generated during towing are properly managed.

The design of a towing chock accommodates the different angles and tensions that may be involved when two vessels are connected, ensuring a firm and stable attachment. It typically features a robust construction to withstand the strain from the towing operation, which is essential for safety and effectiveness while maneuvering another vessel.

In contrast, other options serve different functions. A bollard, for example, is primarily a mooring device secured to the dock, and while it can be used in towing situations, it is not specifically designed for that purpose. The center chock and bow chock are also mooring devices that may not provide the same design advantage or safety features critical in towing scenarios. Therefore, the towing chock is the most suitable choice when the task involves towing another ship.