单项选择题
A.amend
B.repair
C.improve
D.clear
单项选择题 All removals to be reassembled in order()of repairs.
单项选择题 After riveting is completed,the joints on the shell of a vessel are generally made watertight by().
单项选择题 A special device that,when fitted into the rotary table,transmits torque to the kelly and simultaneously permits vertical movement of the kelly to make the hole is called a().