An indirect radar echo is caused by a ...

单项选择题An indirect radar echo is caused by a reflection of the main lobe of the radar beam off the observer’s vessel. Which of the following is NOT a characteristic of indirect echoes?（）.

A.Their bearing is almost constant，even when the true bearing of the contact changes appreciably
B.They always appear on a bearing of 90°from the true bearing of the contact
C.The indirect echoes usually appear in shadow sectors
D.When plotted，their movements are usually abnormal

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2.单项选择题An ECDIS is required to display which information?（）

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4.单项选择题An ECDIS is required to display which information?（）

A.Radar targets
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5.单项选择题A tall object with a light on or near the shore，to act as a guide or warning to mariners is called（）.

A.beam
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6.单项选择题A radar range to a small，charted object such as a light will provide a line of position in which form?（）.

A.Straight line
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7.单项选择题A radar display which is oriented，so that north is always at the top of the screen，is called a(n)（）.

A.relative display
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8.单项选择题A radar display in which North is always at the top of the screen is a(n)（）.

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9.单项选择题A radar contact will remain stationary on a relative motion radar display only when it is（）.

A.on the same course as your vessel
B.at the same speed as your vessel
C.on the same course and speed as your vessel
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10.单项选择题A FICTIVE LINE DISPLAYED ON THE RADAR SCREEN SEPARATING THE FAIRWAY FOR INBOUND AND OUTBOUND VESSELS SO THAT THEY CAN SAFELY PASS EACH OTHER defines（）.

A.Separated line
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