单选题A whistle signal of one prolonged，one short，one prolonged and one short blast，is sounded by a vessel（）.A at anchorB towing a submerged objectC being overtaken in a narrow channelD in distress

On the high seas，a fog signal consisting of one prolonged blast followed by four short blasts would indicate the presence of a ______.

A.vessel being towed

B.fishing vessel engaged in trawling

C.vessel at anchor warning you of her location

D.power-driven pilot vessel on station underway

If you do NOT understand the course or intention of an approaching vessel you should sound ___________.

A.one short blast

B.one prolonged blast

C.not less than five short blasts

D.not less than five prolonged blasts

The emergency signal for fires is sounded on the ship’s whistle and general alarm as _____.

A.a continuous ringing for 10 seconds

B.one short ring followed by one long ring

C.two long rings of at least 20 seconds

D.a continuous ringing until the fire is extinguished

Approaching a anchorage in fog, you hear one short, one prolonged, and one short blast in that sequence on a ship’s whistle. This indicates ______.

A.A vessel towed

B.A vessel not under command and unable to maneuver.

C.A vessel anchored giving warning of her position.

D.A vessel stopped dead in the water.

In which case would an overtaking vessel sound a whistle signal of two prolonged followed by one short blast? ______.

A.When overtaking in restricted visibility

B.When overtaking in a narrow channel

C.When overtaking on open waters

D.When no other vessels are in the immediate area

You are on international waters during a heavy rainstorm and hear a vessel sounding a fog signal of one prolonged blast followed by two short blasts． Which of the following could it be？Ⅰ．A vessel laying submarine cable making way．Ⅱ．A pilot vessel on station at anchor．

A.Ⅰ only

B.Ⅱ only

C.Either Ⅰ or Ⅱ

D.Neither Ⅰ nor Ⅱ