化学变化前后一定发生改变的是
A．原子种类
B．原子数目
C．分子种类
D．元素种类
答案：C
题目分析：化学变化是有新物质生成的变化，化学变化的过程遵循质量守恒定律，化学变化前后原子种类、原子数目、元素种类保持不变；分子种类一定改变。选C。
点评：化学变化过程是分子分解为原子，原子重新组合成新分子的过程，化学变化前后原子种类、原子数目、元素种类保持不变。
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| J.K. Rowling is the writer of Harry Potter, which is now one of the best-sellers in the world. She 1 born in Bristol on July 31st, 1965. She has one sister who is two years 2 than her. Both girls loved 3 to their father read bedtime stories. They especially loved stories about magical (魔幻的) world. Rowling wrote her first story 4 the age of six. On a long train trip in 1990, an idea came to her. She wanted to write about a boy who has magic but he himself doesn't know it. In 1992, Rowling began 5 the first Harry Potter book for young 6 . It appeared in June, 1997. The book was a great success. And the film came out in November, 2001. Now Harry Potter series (系列) is 7 with people of all ages and about sixty 8 books were sold in 200 countries. In this series, Harry is an ordinary boy: polite, friendly, brave and clever. So when children read about Harry, they can imagine being like him. That's 9 Harry Potter series has been so popular. J.K. Rowling is very 10 with the success. Now she's really enjoying life. She says she will go on writing children's books. | ||||
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中国军方多款新型武器装备的展示，引发西方军事专家捕风捉影的各式猜测。