On top of scavenging air box is mounted a strong cast iron frame for each cylinder known as（）
A. cooling jacket
B. cylinder liner
C. piston crown
D. cylinder cover
查看答案
禁止随地吐痰、吸烟、闲谈、接打手机及一切有碍安全的行为，五环路内线路驾驶员可自行开启车厢灯。（）
A. 正确
B. 错误
You want to flash back a test database by five hours.You issue this command:SQL > FLASHBACK DATABASE TO TIMESTAMP (SYSDATE - 5/24);Which two statements are true about this flashback scenario?（）
A. The database must have multiplexed redo logs for the flashback to succeed.
B. The database must be MOUNTED for the flashback to succeed.
C. The database must use block change tracking for the flashback to succeed.
D. The database must be opened in restricted mode for the flashback to succeed.
E. The database must be opened with the RESETLOGS option after the flashback is complete.
F. The database must be opened in read-only mode to check if the database has been flashed back to the correct SC
S700K型电动转辙机不可挤型是工厂将保持联接器内部的弹簧取消，放一个止挡环，用于阻止与动作杆相连的保持栓的移动，成为（）。
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