若消费水平和服务性消费支出均处在平均水平的S市农村居民三口之家,则这个家庭20102013年的服务性消费支出总计约为()万元。
A. 1.4
B. 2.5
C. 4.2
D. 5.1
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听力原文:M: Why didn’t you stop when we first signaled you at the crossroads? W: Sorry,
I was just a bit absent-minded. Anyway, do I have to pay a fine? Q: What do we learn from
the conversation?
A. The woman had been fined many times before.
B. The woman knows how to deal with the police.
C. The woman had violated traffic regulations.
D. The woman is good at finding excuses.
某三年级制普通初中连续六年的在校生人数分别为:X1,X2,X3,X4,X5,X6,假设该校所有学生都能顺利毕业,那么前三年的入学学生总数与后三年的入学学生总数之差为()。
A. (X1+X2+X3)-(X4+X5+X6)
B. X1-X4
C. X3-X6
D. (X3-X1)-(X6- X4)
用氢火焰离子化检测器检测废水中的酚,记录仪的灵敏度为0.2mV·cm-1,记录仪纸速为1cm·min-1,进样量2μL,苯酚标样浓度2mg·mL-1。测得色谱峰面积为5.28cm2,三倍噪音信号为0.1mv。求该检测器对苯酚的灵敏度和检出限。
气相色谱仪一般由______、______、______、______、______和______组成。