倡导“低碳生活”,应减少排放的气体是( )
A:氧气
B:二氧化碳
C:氮气
D:水蒸气
— The boy can speak both English and Japanese he is only ten.
— Wow, what a clever boy!
—He works in a hospital.
人的上臂以肩关节为枢纽,可做伸屈、旋转、换转等各种动作.这说明关节在运动中起什么作用( )