探月工程总设汁师，为中国航天事业做出突出贡献的科学家孙家栋；高铁焊接师，为“中国制造”由大变强助力的“大国工匠”李万君；河北农业大学教授，把毕生精力投入到山区生态建设和科技富民实业之中的全国脱贫攻坚模范李保国，这些时代英雄共同的精神追求是（    ）

    Have you ever picked up a pen to write some characters, but you can't ____(记得) what they look like?

    You're not alone. CCTV-10 started a show ____(叫做) Chinese Character Dictation Com-petition (《中国汉字听写大会》) last year. On the show, only three out of 10 adults____（正确地）wrote bingjiling (ice cream 冰激凌), and no one could   write out penti (sneeze喷嚏). According to a survey, 94.1% of people said they had memory lapses (差错) when ____(写) some characters.

    It seems that Chinese characters are in danger. Since the digital(数码) age began, fewer and ____(少) people use pens and paper. Most people now write Chinese on keyboards using pinyin. As a____(结果), many people would forget the features（特征）of a Chinese character, such as its structure and ____（意思）easily.

    Chinese characters are one of the world's____（古老的）written languages, dating back (追溯到) to 1100 BC. It's not only a way for us to record things,____（而且）it's important to pass on Chinese culture. For example, the character nan (male男) is made up of two____(部分), tian (farmland田) and li (strength力). We can tell from it that in the old times Chinese men were in charge of (负责) working on the farmland.

某物体的质量为810g，体积是300cm³，将其截去一半，它的密度为____ kg/m³，水的密度是____kg/m³，它表示____