A:木球受到的浮力最大
B:铁球受到的浮力最大
C:铜球受到的浮力最大
D:三个球受到的浮力一样大
— Listen! Someone is knocking at the door. Who can it be?
— It _______ be Tom. He said he would visit me this evening.
如果一个圆锥的母线长为4,底面半径为1,那么这个圆锥的侧面积为____ .
如图所示,是A、B两质点从同一地点运动的s﹣t图象,则下列说法正确的是( )