中国人民大学副教授孟宪实在《百家讲坛》作了“太宗继位”“魏征进谏”“以民为本”等系列讲座。由此推知他所讲的主题是（    ）

用分数表示图中涂色部分．

①____

②____

③____

④____

下列现象中只有动能的是（  ）

阅读下面的短文,在空白处填入一个适当的词,或填入括号中所给单词的正确形式。
    Peter is ____ really interesting boy. This is his tree house. It's very cool. Look! What's that next to the desk? It's Peter's dog. ____(it)name is Angelina. It's a funny dog. It can____(smile). There's a radio and some picture____(book)on the desk.  Look at the wall.  You can see a map of America and a clock on it. Peter usually____(go)to his tree house at weekends with his friends. They play games and have a good time there.

（1）人类的生活离不开金属材料．生活中某些食品包装内放一小包铁粉，作用是什么？

（2）某同学在探究铝与稀盐酸的反应时，发现打磨过的铝片反应比未打磨过的铝片反应剧烈，请解释原因可能是什么？

（3）将一定量的锌粉加入到氯化亚铁和氯化铜的混合溶液中，充分反应后过滤，向滤渣中加入稀盐酸，无气泡产生．请分析滤液中所含溶质情况？