单项选择题 The angle measured at the observer’s meridian from the elevated pole，clockwise or counterclockwise up to 180°，to the vertical circle of the body is the（）.

单项选择题 The angle at the pole measured through 180°from the prime meridian to the meridian of a point is known as（）.

单项选择题 The altitude at LAN may be observed by starting several minutes in advance and continuing until a maximum altitude occurs. This procedure should not be used（）.