premise: Serial serum <mask> levels remained normal ; the serum glutamic oxaloacetic transaminase was 10 units per ml. per min. .
hypothesis: the proper context for <mask> here should be a light soft silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water; is abundant in nature in combined forms occurring in sea water and in carnallite and kainite and sylvite