通常土壤含氮量为（）
A.0.01℅-0.0.5℅
B.0.01℅-0.02℅
C.0.01℅-1℅
D.0.01℅-0.5℅
参考答案：D
It was by making great efforts ____ she caught up with other students. [ ]
A. how
B. when
C. what
D. that
吞咽困难或昏迷患者留置胃管的护理方法有哪些？
