如图所示，长方形内有两个相邻的正方形，面积分别为4和2，那么阴影部分的面积为（      ）

金砖五国联手，谋求共赢发展阅读资料，完成下列各题。

资料一：金砖五国由巴西、俄罗斯、印度、南非和中国组成。金砖国家领导人第三次会晤于2011年4月14日在我国海南省三亚市举行，主题是“展望未来、共享繁荣”，议题包括国际形势、国际经济金融问题、发展问题以及金砖国家合作。金砖国家国土面积占世界领土面积近30%，人口占世界的42%，2010年五国国内生产总值约占世界总量的18%，贸易额占世界的1 5%。五国联手后，其经济发展前景将更加美好。

资料二：金砖五国位置图（图）。

1898年7月居里夫妇发现了一种放射性极强的元素，为了纪念自己的祖国波兰把这种新元素定名为钋，同时由于对放射性的研究获得了诺贝尔物理学奖．吸烟有害健康，香烟中含有钋210，₈₄²¹⁰Po是一种很强的放射性同位素，为了探测放射线的性质，真空室中在放射源钋210的对侧放有一荧光屏，可以根据荧光屏上的打点情况来检测放射线的强弱．

阅读理解

    Children with no shoes on do better at school than those with shoes on，a study suggests．

    For over 10 years，researchers from universities observed （观察） children in 100 schools from 25 countries．They found that classrooms were quieter when children took off their shoes．It provided a quieter environment where pupils were more willing to focus on study than those with shoes on．

    "Children are much more willing to sit on the floor and relax if they have no shoes on，"said professor Stephen Heppel，a lead researcher．

    "The last place a child would sit to read is an upright chair．And we've found that 95% of them really don't read on a chair at home，"Heppel added．"When they go on holidays，they read lying down．"Professor Heppel hopes to bring the"shoeless policy"to all U．K．schools．He says relaxing conditions at school make children feel as if they're at home．He believes all the teachers will be glad to adopt the habit．