关于叶酸的描述，下列哪项是正确的（）
A.不耐热
B.在酸性环境中不稳定
C.存在于绿叶蔬菜、水果和动物内脏等食品由
D.每天需要约100μg
E.以上都是
参考答案：E
解析：叶酸为淡黄色晶体粉末，微溶于水，不溶于乙醇、乙醚等有机物质，对热、光线、酸性溶液均有不稳定性。广泛存在于绿色蔬菜、水果和动物内脏。由动物实验推算出的需要量为一日0.1～0.2mg。
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| When I was ten, my family moved to a housing project in East Los Angeles. Even though we struggled to make 1 meet, my parents stressed to me 2 fortunate we were to live in a great country with 3 opportunities. They imbued(灌输) in me the 4 of family, faith and love for our country. The following year, my dad, Benjamin, injured his back working in a cardboard-box factory and was 5 as a hairstylist. He rented space in a shopping mall and gave his shop the fancy name of Mr Ben's Coiffiure. The owner of the shopping center gave Dad a discount on his 6 for cleaning the parking lot three nights a week, which 7 getting up at 3 a.m. To pick up trash, Dad used a little machine that looked like a lawn mower (割草机) 8 Mom and I emptied garbage cans and picked up litter 9 I did this job for two years, but the lessons I learned have 10 a lifetime. I learnt discipline, a strong work ethic and a 11 attitude towards life, I also learned at an early age the importance of 12 life's competing interests-in my 13 , school, homework and a job. All 14 helped during my senior year of high school, when I worked 40 hours a week at a fast-food restaurant while 15 precollege courses. The hard work paid off. I attended the U.S. Military Academy and went on to get graduate 16 in law and business from Harvard, 17 I joined a big Los Angeles law firm. In these jobs and in everything else I've done, I have never forgotten those days in the parking lot. The experience has 18 me that there is dignity(尊贵) in all work and that if people are working to 19 themselves and their families, that is something we should 20 . | ||||
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