A.30° B.45° C.60° D.90°
A.加適量蒸溜水 B.加適量甘油 C.加適量安息酸或硼砂 D.用比重計(jì)證實(shí)支承液比重不對(duì),加適量甘油
A.檢查過(guò)去某段時(shí)間的航向 B.判斷羅經(jīng)的性能 C.讀取航向并加記錄