A.the chain is not upright B.the chain is tight C.the chain is upright D.the chain is slack
单项选择题I hereby request permission（）the ship’s main engine for routine maintenance.
A.immobilize B.to immobilize C.immobilization D.immobilizing
单项选择题I haven’t seen the Harbor Officer（）.
A.yet B.still C.already D.just now
