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蛋白质在人体胃肠内与水反应，最终生成氨基酸被人体吸收．丙氨酸（化学式为C3H7O2N） 是其中的一种，请回答下列问题： （1）丙氨酸的相对分子质量是 ． （2）一个丙氨酸分子中含有 个原子． （3）356g丙氨酸中含氮元素的质量多少克？（写出计算过程） 答案：【考点】相对分子质量的概念及其计算；化合物中某元素的质量计算． 【专题】化学式的计算． 【分析】（1）根据相对分子质量为组成分子的各原子的相对原子质量之和，进行分析解答． （2）根据一个丙氨酸分子的构成进行分析解答． （3）根据化合物中某元素的质量=该化合物的质量×该元素的质量One thing that British and Chinese cultures share is a love for fine tea. Today, when we think of Western tea culture, we often think of the English and beautiful china tea cups. Afternoon tea People believe that an English lady, Anna, first introduced the idea of afternoon tea. In the 18th and 19th centuries. the English ate only two main meals each day ,breakfast and a heavy supper that would last for several hours in the evening. As a result, people often got very hungry during the long wait between these two meals. To solve this problem, Anna came up with the clever idea of inviting some friends to join her for an afternoon meal between four and five o'clock. This meal included cakes and sandwiches. and tea was served(提供)to wash down the food. In order to make this afternoon meal important, fine china cups and plates, and silver teapots. knives, forks and spoons were used .Soon, afternoon tea parties became popular social occasions. Today, afternoon tea parties continue to play an important part in the social life in modern Britain. Will you come for coffee? Coffee also has an important role in British culture. People often use the words“Will  you come for coffee?” to mean “Would you like to come to my home for a chat?” Normally, several different drinks such as tea, hot chocolate or a soft drink like orange Juice will be served as well as coffee. and you will be asked what you would like. However, you will not normally be offered wine at a "coffee" party. Coffeehouses and the London Stock Exchange In the 17th century London, coffeehouses were busy and noisy places. Businessmen and  bankers went to coffeehouses to do their business, as well as to drink coffee. In fact, the London Stock Exchange(股票交易所) is believed to have started from these coffeehouses  1. Anna introduced the idea of drinking afternoon tee because she _______. A enjoyed chatting with her friends at home B loved fine tea and beautiful china tea cups C. wanted to share nice food with her friends D found people felt hungry during the long wait between the two meals 2.What does “social occasions” mean in Chinese? A．集体婚礼 B．社交活动 C．社区表演 D．公共场合 3.f someone says to you “Will you come for coffee?”, you _______. A．will be offered coffee only B．are asked what you would like to drink C．will be asked to have a chat with him or her D．are invited to take part in an afternoon tea party 4.From the last paragraph (段落) we can see _______. A. a new business was started in coffeehouses B. coffeehouses are still used by businessmen and bankers C. businessmen and bankers went to coffeehouses just for coffee     D. most people wouldn’t like to go to coffeehouses because of the noise