单项选择题 Where will you find the requirements for the signals that must be sounded by a mobile offshore drilling unit that is being towed through an area of restricted visibility? （）

单项选择题 What is the period of validity of the SOLAS required Cargo Ship Safety Construction Certificate? （）

单项选择题 To determine what navigation lights and day-shapes must be displayed on mobile offshore drilling units under tow，you should check the（）.