31. 治療細菌性肺炎前進行痰液培養，所收集到的「痰液檢體」符合下列哪一描述條件時，為較適當的檢體？( 單位為 cells per low-power field ) (A) ＞25 neutrophils and＞10 squamous epithelial cells (B) ＞25 neutrophils and＜10 squamous epithelial cells (C) ＜25 neutrophils and＞10 squamous epithelial cells (D) ＜25 neutrophils and＜10 squamous epithelial cells