如图所示,在O点处放置一个正电荷。在过O点的竖直平面内的A点,自由释放一个带正电的小球,小球的质量为m、电荷量为q。小球落下的轨迹如图中虚线
如图生态系统中的能量最终来源于 A.植物 B.动物 C.微生物 D.太阳
下列有关洗涤的说法中错误的是( ) A.用汽油溶解衣物上的油渍 B.用热的纯碱溶液洗去菜刀上的铁锈 C.用食醋洗去热水瓶中的
Perhaps it will never be known __________ he did with those materials on the incident. A.that B.what C.which D.how
根据短文意思,用方框中所给词语的适当形式填空 (其中两个多余选项)。 happy, thin, his old friends, playing chess, wear glasses, straight, read newspaper, healt
“It hurts me more than you”, and “This is for your own good” —these are the statements my mother used to make years ago when I had to learn Latin, clean my room, stay home and do homework.
如图可以看作是一个等腰直角三角形旋转若干次而生成的,则每次旋转的度数是_______
图3为“影响工业区位的劳动力因素、科技因素和其它因素的三角坐标图”。回答28—29题。 28.序号①代表的工业企业可能是