Which type of volcano is considered unlikely to ever erupt again?

The type of volcano considered unlikely to ever erupt again is an extinct volcano. An extinct volcano is one that has not erupted in a significant period of time and is not expected to erupt again in the future due to the cessation of volcanic activity. This typically means that there has been no eruption for thousands to millions of years, and there is no geological evidence suggesting that it may become active again.

In contrast, an active volcano is one that is currently erupting or has erupted recently, while a dormant volcano is one that has not erupted for a long time but is still considered capable of erupting in the future. Volcanic mountains, which can consist of various types of volcanoes, do not inherently indicate whether they will erupt again or not. Therefore, the classification of a volcano as extinct implies its complete inactivity and the unlikelihood of future eruptions, making it the correct answer to this question.