国家标准中，把牙型角α＝55°的三角形米制螺纹称为普通螺纹。
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支气管哮喘发作有哪些先兆症状？静脉推注氨茶碱的注意事项？
Which of the following are steps to configure destination-based Remote Triggered Black Hole（RTBH）filtering？（）
A. Configure OSPF between trigger router and black hole routes
B. Configure all edge routers with static （reserved） host route to Null0
Configure BGP beteen trigger and black hole routers
D. Configure on trigger router to advertise victim host route with commumity
E. Activate black hole by redistributing route for victim into BGP with next-hop set to the static（reserved）host route configured on edge router
法兰垫片的作用时（）。
A. 增强法兰
B. 防止法兰生锈
C. 密封法兰缝隙
D. 连接法兰
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