47.某犬長期下痢，檢驗其血中之維生素，若維生素B12（cobalamin）下降而葉酸鹽（folate）上升，則可列入考慮的疾病有那些？①exocrine pancreatic insufficiency ②small intestinal bacterial overgrowth ③distal small intestinal disease ④proximal small intestinal disease (A)①② (B)①③ (C)②④ (D)②③