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.

若向量$\overrightarrow{a}$，$\overrightarrow{b}$满足|$\overrightarrow{a}$|=1，|$\overrightarrow{b}$|=2且|2$\overrightarrow{a}$+$\overrightarrow{b}$|=2$\sqrt{3}$，则向量$\overrightarrow{a}$，$\overrightarrow{b}$的夹角为（　　）