桑基、蔗基、果基鱼塘是珠江三角洲地区传统的农业景观和被联合国推介的典型生态循环农业模式。改革开放以来，随着工业化和城镇化的快速发展，传统的基塘农业用地大部分变为建设用地，保留下来的基塘也变为以花基、菜基为主。据此完成以下问题。 

我国为了扩大内需，执行了积极的财政政策，财政支出逐年增加，财政赤字也有所上升。但是伴随着2010年物价的持续上涨，我国相对减少了财政赤字。下面关于财政赤字的说法正确是                  （   ）

小明设计了一种照明电路图，其设计要求是：S₁、S₂分别为楼上和楼下的开关（都是单刀双掷开关），要求拨动其中任一开关，都能改变电灯原来的发光或熄灭状态。图所示的四幅电路图中，既符合上述设计要求，又符合安全用电要求的是（  ）

阅读理解
    Different weather makes people feel different．It influences health，intelligence and feelings．
    In August，it is very hot and wet in the south the US．People there have heart trouble and other kinds of health problems during this month．In the Northeast and the Middle West，it is very hot in the summer and very cold in the winter．People in these states have more heart trouble after the weather changes in February or March．
    The weather can also influence intelligence ． For example，in a 1983report by scientists，IQ(智商)of a group of students was very high when a very strong wind came, but after the strong wind,
    Their IQ was 10% lower than before. The wind can help people have higher intelligence. However,very hot weather can make it lower. Students in many schools of the US often get worse in exams(考试)in the hot months of the year(July and August).
    Weather also has a strong influence on people's feelings．Winter may be a bad time for thin people．They usually feel cold during these months．They might feel unhappy during cold weather．But fat people may have a hard time in hot summer．At about 18℃people become stronger．Low air pressure may make people forgetful．People leave more bags on buses and in shops on low-pressure days．
    Are you feeling sad，tired，forgetful，or unhappy today？It may be the weather's problem．

如图所示，甲为一半径为R的光滑的 $\frac{1}{4}$ 圆弧槽，其底端A点与一粗糙的水平面相连接，将重为G的物体从斜面顶端由静止释放，滑到A点时所用时间为t，由于受到滑动摩擦力的作用物体最终静止在距A点距离为s的B点．求：