Concept:Aneroid barometers are preferred for aircraft altitude measurement because they are compact and portable.Explanation:Aneroid barometers do not use liquid mercury.They contain a small metal capsule that expands and contracts with air pressure.This allows them to be built small and lightweight.In an aircraft, space and weight are limited, so a small and convenient instrument is essential.The barometer measures altitude indirectly from the changes in atmospheric pressure.Answer:B. Small and convenient