压力容器在正常使用压力范围内，无塑性变形的情况下，突然发生的爆炸称为（）
A.塑性破裂
B.脆性破裂
C.疲劳破裂
D.蠕变破裂
参考答案：B
单项选择。
What does your father do? [ ]
A. He's teaching.
B. He's at school.
C. He's a teacher.
D. He doesn't teach Chinese.
准同步并列的实际条件中，对频率差的要求是不大于（）
A.0.1～0.25Hz
B.0.25～0.4Hz
C.0.4～1.0Hz
D.1.0～2.0Hz
