下列物质属于电解质的是（　　）

下列几个纬度中，地球自转线速度最大的是

欧阳修、苏洵等众多学者提倡敬宗收族、义恤乡里；范仲淹创有范氏义庄赡养族人，各地士绅纷纷效仿，办有“义仓”、“义学”、“义冢”等等。这一风气逐渐盛行的主要原因是（　　）

根据短文理解完成下列各题。
C
    Tom is a junior high student. He is good at some subjects but his favourite subject is chemistry. Yesterday he met some trouble when he had his chemistry class.
    At that moment, Tom was doing an experiment in class. He tried twenty times, but he couldn't succeed. So he decided to stop doing the experiment. He felt really unhappy.
    His teacher came up to him and asked why he was unhappy. Tom said, "All my work is in vain (白费力气). I fail twenty times and I get nothing."
    Tom's teacher touched Tom's head with a smile. He said to Tom, "Oh, you do a lot and you can get a lot from the mistakes. At least, you know that there are twenty ways you can't use to do this experiment."
    After hearing the teacher's words, Tom became excited. He kept doing the experiment, improved his methods, and he succeeded at last.

改错题（每小题有一处是错误的，请指出错误并订正或说明理由）
（1）在全国基本上消灭了剥削和剥削阶级是在土地改革完成后。 ____             
（2）曾有报刊不切实际地提出“人有多大胆，地有多大产”的口号。这种宣传应该是出现在三大改造时期。  ____               
（3）“文化大革命”结束的标志是粉碎林彪反革命集团。  ____                 
（4）1949年10月，三大改造的基本完成，标志着中国人民从此站起来了，成为国家的主人。____                         
（5）小李的爷爷是位革命老同志，他晚年写回忆录：“……1954年，我参加第一届中国人政治协商会议，大会热烈通过《中华人民共和国宪法》。这是一部社会主义新宪法，它规定：一切权力属于人民”。____