单项选择题
A.why B.when C.how D.what
If the hatch cover does not move, （）should be checked.A...
单项选择题If the hatch cover does not move, （）should be checked.
A. the open valve B. the stop valve C. the steam valve D. the close valve
To ensure the safety in operating hatch covers, oil the...
单项选择题To ensure the safety in operating hatch covers, oil the moving parts （）.
A. monthly B. every three months C. once monthly D. every two months
During operation, the （）should check the working condit...
单项选择题During operation, the （）should check the working condition of the derrick.
A.foreman B.operator C.opener D.stevedore
