螺纹紧固件由专门的工厂批量生产，在设计中只需确定紧固件的名称、规格、标记，以便购买选用。
查看答案
螺纹紧固件各部分尺寸可以从相应的国家标准中查出，但在绘图中为了简便和提高效率，一般不必查表绘图而采用比例画法。
A. 对
B. 错
开槽沉头螺钉的头部锥角是120°
A. 对
B. 错
Conversation 1[音频]
A. The band was terrible.
B. The weather was cold.
C. He was too sick to go.
D. He went to the concert before.
Conversation 2[音频]
A. She didn't go to the interview at all.
B. She preferred to talk about the interview later.
C. She didn't feel like talking about the interview.
D. She looked forward to having the interview.
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