人在平静状态时,完成吸气动作需要( )。
A:肋间外肌收缩,膈肌收缩
B:肋间外肌舒张,膈肌舒张
C:肋间外肌收缩,膈肌舒张
D:肋间外肌舒张,膈肌收缩
Who is good at swimming? -