Final answer:
The term 'village' is used to correctly complete the statement about Alderdale lying beneath a lake formed by the John Day Dam.
Step-by-step explanation:
The word that correctly completes the statement “Alderdale, a village now lies quiet and still beneath the lake formed by John Day Dam” is “village”. In the given context, the term refers to a small settlement that has been submerged due to the creation of a dam, which causes the nearby river to expand into a lake, covering the area where the village once stood.