单项选择题
A.a not knowing B.an unknowing C.an unknown D.a not known
Anchors are prevented from running out when secured by ...
单项选择题Anchors are prevented from running out when secured by the（）.
A.brake B.devil's claw C.pawls D.All of the above
An LWT anchor often has difficulty tripping in（）.A.sand...
单项选择题An LWT anchor often has difficulty tripping in（）.
A.sand B.soft soil C.stiff clay D.heterogeneous soil
An integral part of a blowout preventer that serves as ...
单项选择题An integral part of a blowout preventer that serves as the closing element on an open hole，and whose ends do not fit around the drill pipe but seal against each other and shut off the space below completely is the（）.
A.shear ram B.blind ram C.pipe ram D.annular ram
