化学与科学、技术、社会、环境密切相关．下列说法不正确的是
A．锂可用于制造质量轻、电容量大的可充电电池
B．“地沟油”经过加工处理后，可以用来制肥皂和生物柴油
C．生石灰、铁粉、硅胶是食品包装中常用的干燥剂
D．太阳能电池板中有高纯硅单质，光导纤维的主要成分是二氧化硅
答案：C
题目分析：A．锂相对原子质量为7，是所有金属中最轻的金属，单位质量产生的电能多所以可用于制造质量轻、电容量大的可充电电池。正确。B．“地沟油”主要成分是各种植物油、动物油，经过提炼、加工处理后，可以用来制肥皂和生物柴油。正确。C．生石灰、硅胶有吸水性，是食品包装中常用的干燥剂，而铁粉则是食品中的防氧化变质的试剂。错误。D．太阳能电池板中材料是高纯硅单质，而光导纤维的主要成分则是二氧化硅，尽管都是含Si元素的物质，但成分不同，性质也不同。正确。
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| Jenna, a popular girl from Westwood Middle School, had graduated first in her class and was ready for new 1 in high school. 2 , high school was different. In the first week, Jenna went to tryouts (选拔赛) for cheerleaders (拉 拉队队员). She was competing against very talented girls, and she knew it would be 3 for her to be selected. Two hours later, the 4 read a list of the girls for a second tryout. Her heart 5 as the list ended without her name. Feeling 6 , she walked home carrying her schoolbag full of homework. 7 home, she started with math. She had always been a good math student, but now she was 8 . She moved on to English and history, and was 9 to find that she didn't have any trouble with those subjects. Feeling better, she decided not to 10 math for the time being. The next day Jenna went to see Mrs. Biden about being on the school 11 . Mrs. Biden wasn't as enthusiastic (热情) as Jenna. "I'm sorry, but we have enough 12 for the newspaper already. Come back next year and we'll talk then." Jenna smiled 13 and left. "Why is high school so 14 ?" she sighed (叹气). Later in 15 class, Jenna devoted herself to figuring out the problems that had given her so much 16 . By the end of class, she understood how to get them right. As she gathered her books, Jenna decided she'd continue to try to 17 at her new school. She wasn't sure if she'd succeed, but she knew she had to 18 . High school was just as her mom had said, "You will feel like a small fish in a big pond 19 a big fish in a small pond. The challenge is to become the 20 fish you can be." | ||||
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