简述自动苏生器操作的步骤？
参考答案：
安置伤员、清理口腔、清理喉腔、插口咽导气管、人工呼吸、调整人工呼吸频率、氧吸入、氧气的准备。
—We don't know ______.
—It is said that he was born in America. [ ]
A. what is he
B. if he lives here
C. where he comes from
D. which country is he from
混凝土采用插入式振捣器分层浇灌时，每层的厚度不应超过振捣棒作用部分长度的（）倍。
A、1.25
B、1.5
C、2
D、2.5
