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问题 选择题

氢气与氧气反应生成水的反应过程中，氢气与氧气的质量之比是（　　）

A．1：1

B．2：1

C．2：32

D．4：32

答案

氢气和氧气在点燃的条件下生成水，方程式为：2H2+O2

点燃
.
2H2O；各物质间的质量之比为2×（1×2）：16×2：2（1×2+16）=4：32：36；所以，氢气与氧气的质量之比是4：32．

故选：D．

问答题

In January 2010 Ami took over an old warehouse with the intention of opening an art gallery. As the warehouse had to be converted, Ami entered into two contracts, one with Bry to do all the necessary plastering and one with Cis, who was to do all the necessary painting. Both Bry and Cis were to be paid €5,000. Both received initial payments of €1,000 and agreed to have the work completed on 31 March, as the art gallery had to be ready for its fi rst exhibition on 1 May.At the end of February, Bry told Ami that he would not complete the plastering in time unless she agreed to increase his payment by a further €1,000. Ami agreed to pay the increased sum in order to ensure that the job was done on time. She then thought it was only fair that she should increase the amount of money promised to Cis by the same amount.However, on completion of the work on time Ami refused to make either of the additional payments to Bry or Cis, beyond the original contractual price.Required:Advise Bry and Cis whether they have any rights in law to enforce Ami’s promise to pay them an extra €1,000. (10 marks)
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多项选择题 X型题

下列细菌中产生肠毒素的是（）

A.白喉棒状杆菌

B.化脓性链球菌

C.痢疾志贺菌

D.金黄色葡萄球菌

E.腊样芽胞杆菌
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