a,b在数轴上的位置如图,化简|a+b|的结果是( )
A:﹣a﹣b
B:a+b
C:a﹣b
D:b﹣a
— It seems that Mr. Wu is standing there.— It ______ be him because he called me from Canada just now.
a、b、c三盏灯分别标有“110V 20W”、“220V 40W”、“36V 60W”的字样,三盏灯都正常发光,比较它们的亮度( )
用大小不同的甲、乙两个力拉同一物体,两力所做的功W与这两个力的方向上移动的距离s的关系图象如图,由图可知,甲乙两个力的大小关系是:F甲____ F乙.