练习曲线可反映动作技能形成过程中三种练习进步状况，即练习进步先快后慢;练习进步先慢后快和__________。
参考答案：练习进步前后一致
Those ____ want to go please sign their names here.
A．whom
B．which
C．who
D．when
空预器吹灰辅汽供汽门的动力源取自何处？
