A:1使关节灵活
B:4使关节牢固
C:2为关节囊
D:1的外面有韧带等结构
— What's it in the bottle?
— It is full of water.
如图所示,将两个相同的弹簧测力计的挂钩挂在一起,然后用方向相反、大小为20N的两个力拉弹簧测力计,则两个弹簧测力计的示数分别为F左=____,F右=____。
—_____ Even though the weather is very bad.