若$a,b,c\in R,a>b$，则下列不等式成立的是            (    )  

下列是我国地形特征之一是（   ）

郑和七下西洋是世界航海史上的壮举，比欧洲航海家早了半个多世纪，他在1405年

从____出发，最远到达____沿岸和____东海岸。

阅读理解A

    Hello,everybody!Look at this picture．This is a nice Sunday afternoon．My family are having a great time．
    I am Bob．I am having bread and listening to my father telling me a story from the newspaper．He thinks it's interesting．Look at my mom．She is listening to the radio．She likes music on it．My two sisters Rose and Sally are plying．Rose is only one year old and Sally is three.My grandpa is having a nap(打盹)．He always has a nap when he has nothing to do．My grandma is drinking a cup of tea．She likes her tea with a lot of milk in it．My cousins are busy．Ken is watering the flowers(浇花)and Mike is cleaning the windows(窗户)．Where is my pet cat Pussy? Oh, it is running after the birds．
    I really like an afternoon like this．
根据材料内容选择最佳答案。

2009年2月9日，加拿大麦吉尔大学卫生中心研究所杰纳斯•雷克研究小组认为，肿瘤细胞能释放一种叫微泡的“气泡”，让肿瘤与血管内皮细胞进行交流，并改变这些内皮细胞的行为．这些微泡在离开肿瘤组织时携带一种特殊的癌症蛋白．当微泡与内皮细胞融合后，它们所携带的癌症蛋白就会促进异常血管形成．这些异常血管向着肿瘤方向生长并为它们提供生长所需营养．下列叙述中不合理的是（    ）