问题
选择题
在下 * * 个反应中，过氧化氢(H2O2)所起的作用是
①H2O2+H2S===2H2O+S↓ ②2H2O2 
2H2O+O2↑ ③H2O2+C12==2HCl+O2↑
A．均是氧化剂
B．均是还原剂
C．均既是氧化剂又是还原剂
D．三个反应中所起作用各有不同
答案
答案：D
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在下 * * 个反应中，过氧化氢(H2O2)所起的作用是
①H2O2+H2S===2H2O+S↓ ②2H2O2 2H2O+O2↑ ③H2O2+C12==2HCl+O2↑
A．均是氧化剂
B．均是还原剂
C．均既是氧化剂又是还原剂
D．三个反应中所起作用各有不同
答案：D
| 根据短文内容选择适当的单词，并用其正确形式填空，每个词限用一次。 | |
in Egypt, the 1. _ favorite game was throwing stones.But a badly thrown stone could 2. _ a child. Looking for something less 3. _ to throw, the people in Egypt 4. _ the first balls. At first, they used tree 5._____to make balls. They used vines ( 藤) to keep the leaves together. Later they began to use pieces of animal skin to make balls and 6. _ them with some light things. These balls were much 7. _ than the old one. Before long they invented a lot of ball games, and 8. _ had its own rules. They began to play these ball games according to the rules. They thought that ball playing was one of the best 9. _ to teach the young men to be brave and 10. _ . |