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（）.

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?（）.

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)（）.