A:being watered; doesn’t need to
B:watering; doesn’t need to
C:to water; needn’t
D:to be watered; needn’t to
如图是平静呼吸时相关结构变化示意图,Ⅰ、Ⅱ表示胸骨和肋骨运动的过程.吸气时肋骨间的肌肉的状态、运动的过程和肺内气压分别是( )
tan300°=____