Positive SSL
1 120. 一縱角度盤是天頂距式之經緯儀,如正鏡讀得天頂距為89°10'20",設垂直度盤無誤差,則倒鏡觀天頂距讀數為
A 0 ° 4 9 ' 4 0 "
B 9 0 ° 4 9 ' 4 0 "
C 1 8 9 ° 4 9 ' 4 0 "
D 2 7 0 ° 4 9 ' 4 0 "