如图,直线a与直线b交于点A,与直线c交于点B,∠1=120°,∠2=45°,若使直线b与直线c平行,则可将直线b绕点A逆时针旋转____
His family__________ all very kind and friendly. His family__________ a happy one.
互为同素异形体的一组物质是( )
磁铁隔着下面哪种物体还能吸引铁?( )