单项选择题
A large basin cut into the shore，closed off by a caisson，and used for dry docking of ships is known as a（）.
A.slipway B.graving dock C.ground warp D.caisson dock
单项选择题 A jack-up drilling unit elevated on the Outer Continental Shelf must have a fog horn that will sound（）.
单项选择题 A jack-up drilling rig being towed must（）.
单项选择题 A helmsman receives the command “Right 15 degrees rudder.”The helmsman’s IMMEDIATE reply should be（）.
