单项选择题
A yellow signal floating in the air from a small parachute，about 300 feet above the water，would indicate that a submarine（）.
A.has fired a torpedo during a drill B.is about to rise to periscope depth C.is on the bottom in distress D.is disabled and unable to surface
单项选择题 Which statement is TRUE concerning the danger signal?（）.
单项选择题 In the safety communication，you can get your R/O（）it for you.
