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问题 选择题

在硫酸（H2SO4）中含有[ ]

A．一个氢分子、一个硫原子、四个氧原子

B．二个氢元素、一个硫元素、四个氧元素

C．两个氢原子、一个硫原子、四个氧原子

D．氢元素、硫元素和氧元素

答案

答案：D

单项选择题

A certain prosthodontist specializes in implanting gold and silver teeth in his patients’ mouths. He charges $650 for a gold tooth and $325 for a silver tooth. If his total fees for implanting gold and silver teeth last week were $15,925 in total, and he implanted five more gold teeth than silver teeth, how many teeth in total did he implant over the week ？（）

A. 31

B. 32

C. 33

D. 34

E. 35
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判断题

割伤主要是由于使用刀具和电动设备不当引起。
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