A:水平恒力F1和F2大小之比为1:2
B:刚撤去F1时刻和恰好回到出发点时刻物体的速率之比为1:3
C:F1和F2对该物体做功之比是1:3
D:F1、F2对该物体做功的最大功率之比是1:3
His leg was badly injured in the accident and it still ______ the marks.
下列材料属于复合材料的是( )