脊髓损伤患者容易合并（）
A.肺水肿
B.心动过速
C.呼吸急促
D.心跳骤停
E.血压升高
参考答案：A
In our class, when the bell rang and the teacher closed his book, it was a（）for everyone to stand up.
A．signal
B．chance
C．mark
D．measure
什么是衰减与串音的比率？
