阅读理解
    Dogs are people's friends. They will do anything their masters (主人) ask them to do and they do their duty very well.
    Curly is my black dog. He is big and strong. He is strong enough to carry me on his1 . He likes running and playing with me. He likes to 2my father around in the fields, too.
   One day my father took off his coat. Put it on the ground 3  a big tree and said to Curly. “  4  my coat.”
Curly sat down on the coat. Then my father remembered he had to5dinner for the family.   6 he went home and forgot all about his coat and dog.  
    Late in the evening I 7 my dog and looked for him everywhere in the yard. I called, "Curly, Curly!" But Curly did not answer.
Soon my father wanted something in his coat pocket (口袋). Suddenly he remembered8  he had done. Quickly he went back to the big tree. What do you think he saw? Curly was 9 sitting on the coat! He was afraid someone would take it10 .

A、B、C、D四种可溶性离子化合物，它们的阳离子可能是Na⁺、Mg²⁺、Ag⁺、NH₄⁺，阴离子可能是NO₃^﹣、OH^﹣、Cl^﹣、CO₃^2﹣，分别取相同质量的四种化合物，溶解于水，配成相同体积的溶液，其物质的量浓度由大到小的顺序是A、B、C、D，则四种物质的化学式分别为A____，B____，C____，D____．

根据长江相关知识，完成各题。

鸽子是人们喜爱的一种鸟类，它们具有卓越的飞行本领．鸽子靠什么来导航呢？有人做了一个实验：他在鸽子的颈部系了一块小磁铁后再将鸽子放飞，发现鸽子迷失了方向．请你根据以上现象回答：

（1）这个人设计本实验的目的是为了验证一个什么样的猜想？____ ；

（2）他在做本实验时，在不同时间、不同地点放飞了不同品种的几十只鸽子，这是为了

____ ．

 

有学者认为“16至17世纪的中国，新的经济形态还十分微弱、脆嫩。明朝时期的早期启蒙思想家们先天不足，是有一种时代性的缺陷……是中世纪末期的产物”，对此观点理解正确的是  (    )