What is meant by the term“radio

: The best estimate of the wind direction at sea level can be obtained from observing the direction of the ().

: You hear on the radiotelephone the word“Securite”spoken three times.This indicates that ().

A.Stations not directly involved with the on-going distress communications may not transmit on the distress frequency or channel
B.Stations remaining off the air to safeguard proprietary information
C.Two three-minute silent periods，at 15 and 45 minutes after the hour，that provide a transmitting“window”for distressed vessels to transmit distress alerts using J3E
D.Communications on a distress frequency or channel is banned for 24 hours following the cessation of the distress traffic

: When a vessel sees the other ahead or nearly ahead，by night she could see the masthead lights of the other in a line or nearly in a line or both side lights，()shall be deemed to exist.

A.The Morse code distress series S-O-S repeated 3 times followed by DEand the vessel's call sign
B.A line of blip code on a radar screen outward from the SART's position along its line of bearing
C.A line of blip code on a radar screen inward from the SART's position to its own ship along its line of bearing
D.None of these

: The maximum draft to which a ship can legally be submerged is indicated by the ().

: A large angle of list can be created by which of the following ________.① Negative initial stability;② Off center weight.

: In working out a local apparent noon sight for your latitude，you subtract the Ho from 90°.The 90° represents the angular distance from ().

What is meant by the term“radio silence”().