Which altitude is displayed on the altimeter when set to a specific QNH?

Question

Question Quiz BPL Gas - Balloon Pilot License - Communication

QuizVDS · Accepted Answer

Altitude in relation to mean sea level

QuizVDS · Answer

Altitude in relation to the 1013.25 hPa datum

QuizVDS · Answer

Altitude in relation to the highest elevation within 10 km

QuizVDS · Answer

Altitude in relation to the air pressure at the reference airfield

Id 85 - BPL Gas - Which altitude is displayed on the altimeter when set to a specific QNH?