单项选择题
Apparent altitude is sextant altitude corrected for（）.
A.parallax and personal error B.inaccuracies in the reading and reference level C.visibility and magnitude D.All of the above are correct
单项选择题 An amplitude of the Sun in high latitudes（）.
单项选择题 Altair is found in what constellation?（）
单项选择题 After Venus passes the point of greatest elongation east in its orbit，the first position in which the elongation will be zero is（）.
