Concept:The ferrule is the part of a fibre-optic connector that holds and aligns the fibre.Explanation:The ferrule has a precision central bore that provides the entry passage for the fibre.It also secures the fibre firmly during termination.The ferrule is then fixed to the connector housing to maintain correct alignment.The coupling device is used to join two connectors, while the cable carries the fibre and the housing protects the whole assembly.Answer:C. ferrule