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