平静呼吸时肺内压在下列哪个时相中低于大气压（）。
A.呼气初
B.呼气末
C.吸气初
D.吸气末
E.呼气过程中
参考答案：C
—Why were you late for the class this morning?
—I got up late, so I ______ the first bus.
A. missed B. took C. caught
左心衰竭可能症状有（）。
A.夜间阵发性呼吸困难
B.心悸
C.劳累性呼吸困难
D.严重者可发生端坐呼吸
E.心前区疼痛
