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问题 单项选择题

用户使用操作系统通常有三种方式，它们是终端命令、系统调用命令和

A．计算机指令

B．宏命令

C．作业控制语言

D．汇编语言

答案

参考答案：C

解析：【解析】用户使用操作系统通常有3种方式，它们是终端命令、系统调用命令和作业控制语言。

填空题

合金是至少含有（）种元素的物质。
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问答题

Each year in the United States more people are killed or injured in accidents—at home, at work or school, at play, or while traveling—than were killed or injured in the Vietnam war. In the early 1990s, about half of these accidental deaths were the result of motor-vehicle accidents. Other major causes of accidental deaths were falls, fires, and poisoning. On a worldwide basis, accidents involving motor vehicles are the primary cause of accidental deaths, followed by accidents in industry and in the home.
Efforts to lessen or to eliminate the hazardous conditions that cause accidents are known as safety measures. Safety is a growing concern around the world, and safety skills fire being taken more seriously today than ever before People have Come to realize that safety skills can be learned, and most safety experts agree that it is possible to predict, and take steps to prevent, the majority of accidents. Few accidents simply "happen". Most are caused by ignorance, carelessness, neglect, or lack of skill.
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