Which one of the following creates a permanent joint between the ends of two fibers?

The correct choice is splices, as they serve the purpose of joining two fiber optic cables together to create a permanent connection. This process involves precisely aligning the ends of the two fibers and then either using a mechanical method or a fusion method to bond them securely. A splice ensures minimal signal loss and maintains the integrity of the optical signal passing through the fiber.

In contrast, connectors are devices used to temporarily join two fiber optic cables, allowing for easy disconnection and reconnection as needed. Adapters act as intermediaries that link two connectors of different types but do not create a permanent join. Fusion, while it can refer to a specific method of splicing, typically does not designate the permanent nature of the joint itself; splice covers all methods, including fusion. Therefore, splices accurately describe the permanent joining of fiber ends, making this answer the best choice.