①自尊 ②自卑 ③自信 ④自负
A:①③
B:①④
C:②③
D:②④
m为在水平传送带上被传送的小物体(可视为质点),A为终端皮带轮,如图所示,已知皮带轮半径为r,传送带与皮带轮间不会打滑.当m可被水平抛出时,A轮每秒的转数最少是( )
下列不属于传染病特点的是: ( )
—Can you help me my cat while I am away?
—No problem. Just bring it to my house you leave.