井下安全阀装在海底泥线以下()米左右。
A、300
B、500
C、2500
D、100
参考答案:D
— What is she doing?
— She is ____________ a book. [ ]
A. looking
B. reads
C. reading
调节器扣件铁垫板锚固螺栓扭矩为()N•m。