A.縱絲與視準(zhǔn)軸 B.管水準(zhǔn)軸與視準(zhǔn)軸 C.管水準(zhǔn)軸與橫絲 D.視準(zhǔn)軸與圓水準(zhǔn)器軸
A.向上傾斜 B.向下傾斜 C.水平 D.可能向上傾斜也可能向下傾斜
A.21.4″ B.-21.4″ C.20.6″ D.-20.6″