如图所示的简单机械中,属于费力杠杆的是( )
A:起子
B:镊子
C:钢丝钳
D:订书机
如图,在水槽中有体积相等的甲、乙两个小球,甲漂浮在水面上,乙悬浮在水中.它们所受浮力F浮、密度ρ、受到的重力G和排开水的体积V排的关系错误的是( )
The room is very dirty . It needs _________
— Can you play the piano?
—Yes, I . I often practice it on weekends.