单选题A light characteristic of composite group flashing indicates that there is a(n)（）.A sharp turn in the channelB narrowing in the channel at that pointC junction in the channelD obstruction that must be left to port

A message by flashing light consists of the call，the identity，the text，and the ______.

A.destination

B.answer

C.time

D.ending

The irregular black line around a charted light such as Race Rock Light indicates that it is ______.

A.unwatched

B.surrounded by riprap

C.a minor light

D.constructed on an artificial island

On a chart, the characteristic of the light on a lighthouse is shown as flashing white with a red sector. The red sector ______.

A.indicates the limits of the navigable channel

B.indicates a danger area

C.is used to identify the characteristics of the light

D.serves no significant purpose

In light characteristics expression，“ Oc (2+3)” means______．

A.occulting

B.occasional flashing

C.groupocculting

D.Composite groupocculting

A buoy having red and green horizontal bands would have a light characteristic of ______.

A.group occulting

B.composite group flashing

C.Morse letter A

D.quick flashing

A steep barometric gradient indicates ______.

A.calms

B.light winds

C.strong winds

D.precipitation

Which word indicates color variation in the characteristics of a light?

A.Opposing

B.Changing

C.Reversing

D.Alternating

A list signal of one white light indicates that the vessel is ______.

A.on an even keel

B.listing about 1° to the side the light is displayed on

C.listing over 5°With the light displayed on the high side

D.listing，and the chutes should be directed to the side where the light is displayed

A cardinal mark showing an uninterrupted quick-flashing white light indicates the deepest water in the area is on the ______.

A.north side of the mark

B.west side of the mark

C.east side of the mark

D.south side of the mark