2015•武汉)如图,已知点A(﹣4,2),B(﹣1,﹣2),平行四边形ABCD的对角线交于坐标原点O.
岳阳盛产龙虾.而青色的生虾煮熟后颜色会变成红色.一些同学认为这种红色物质可能就象酸碱指示剂一样,遇到酸或碱颜色会发生改变.就这些同学的看法而言应属于科学探究中的( )
下列几何体中,主视图和俯视图都为矩形的是( )
-- What's wrong, Daming?
-- Oh, I feel sad to hear more than _______ people lost their lives in the earthquake in Sichuan at 2:28 on the afternoon of May 12, 2008.