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问题 选择题

取几粒大理石放入试管，向其中加入足量的酸溶液，开始有气泡产生，一会儿后反应却停止了，可能的原因是（　　）

A．装置漏气

B．加入的是稀盐酸

C．加入的是稀硫酸

D．生成的气体被酸溶解了．

答案

A、若装置漏气，应该是收集不到气体或收集的慢；依据现象开始有气泡产生，一会儿后反应却停止了，不是装置漏气，故A错误．

B、制取二氧化碳的药品是石灰石和稀盐酸，因此加入盐酸是二氧化碳的实验室制法，故B错误；

C、硫酸和石灰石反应，产生的是微溶性硫酸钙附着在固体表面阻碍反应的进一步进行，故C正确；

D、生成的气体是二氧化碳，二氧化碳本身就是酸性气体，所以二氧化碳不溶于酸，故D错误．

故选C．

单项选择题

在ERP中有不同的计划层次，其中（）是将MPS排产的产品分解成原材料采购件的采购计划、外协件的外协计划和各种自制件的加工装配计划。

A．能力需求计划

B．主生产计划

C．企业计划

D．物料需求计划
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单项选择题

Computer programmer David Jones earns ￡35,000 a year designing new computer games, yet he cannot find a bank prepared to let him have a check card. Instead, he has been told to wait another two years, until he is 18.
The 16-year-old works for a small firm in Liverpool, where the problem of most young people of his age is finding a job. David’s firm releases two new games for the expanding home computer market each month.
But David’s biggest headache is what to do with his money. Despite his salary, earned by inventing new programs within fight schedules, with bonus payments and profit-sharing, he cannot drive a car, take out a mortgage, or obtain credit cards.
He lives with his parents in their council house in Liverpool, where his father is a bus driver. His company has to pay ￡150 a month in taxi fares to get him the five miles to work and back every day because David cannot drive.
David got his job with the Liverpool-based company four months ago, a year after leaving school with six O-levels and working for a time in a computer shop. "I got the job because the people who run the firm knew I had already written some programs," he said. "I suppose ￡35,000 sounds a lot but actually that’s being pessimistic. I hope it will come to more than that this year." He spends some of his money on records and clothes, and gives his mother ￡20 a week. But most of his spare time is spent working.
"Unfortunately, computing was not part of our studies at school," he said. "But I had been studying it in books and magazines for four years in my spare time. I knew what I wanted to do and never considered staying on at school. Most people in this business are fairly young, anyway." David added, "I would like to earn a million and I suppose early retirement is a possibility. You never know when the market might disappear.\

He was employed by the company because ______.

A. he had worked in a computer shop
B. he had written some computer programs
C. he works very hard
D. he had learned to use computers at school
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