单项选择题 共阴极数码管中，显示0的代码是（） A、3f B、06 C、5b D、4f

问答题 CA6140车床的主轴电动机运行中自动停车后，操作者立即按下启动按钮，但电动机不能启动，试分析故障原因。

单项选择题 In this section, you will hear three passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D).A、Shipbuilding. B、Logging. C、Aircraft manufacturing. D、Software, biotechnology and Internet.