Question

当吸气时                                                                                                  

A．肋间肌和膈肌收缩	B．肋间肌和膈肌舒张
C．膈肌顶部上升	D．肺内气压增大

Answer 1

A解析:
吸气时，膈肌收缩，肋间肌收缩，胸廓容积变大；呼气时，膈肌和肋间肌舒张，胸廓容积变小。