A:200N
B:60N
C:40N
D:10N
地图三要素是指( )
如图为一小球从A点沿直线运动到F点的频闪照片,若频闪照相机每隔0.2s闪拍一次,分析照片可知:小球从A点到F点做的是____运动(选填“匀速直线”或“变速直线”).其中,小球从B点到D点的平均速度是____ m/s.
下列图例中,表示公路的是( )
—Many people in big cities cannot enjoy life even though they have houses, cars and ideal jobs.
—Sub-health may partially ______ it.