The connected joints of pipe，usually made of three joints of pipe approximately 90 feet long，racked in the derrick when making a trip are called a（）.

An LWT anchor often has difficulty tripping in（）.

In nautical terminology a dog is a（）.

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（）.

In the piping systems of a vessel，what type of valve gives the least resistance to fluid flow when fully open?（）.

The holding capability of an anchor is primarily determined by the（）.

The C02 flooding system is actuated by a sequence of steps which are（）.

In ship construction，frame spacing is（）.

The extension of the after part of the keel in a single-screw vessel upon which the stern post rests is called the（）.

Centrifugal pumps have what advantage(s) over reciprocating pumps?（）.