單項(xiàng)選擇題

設(shè)地面B、B′兩點(diǎn)間相距80m,水準(zhǔn)儀安置在BB′中點(diǎn)時(shí),測得高差hBB=+0.228m;將水準(zhǔn)儀移至離B點(diǎn)附近2-3米處,讀取B點(diǎn)水準(zhǔn)尺上中絲讀數(shù)=1.666m,B′尺上中絲讀數(shù)=1.446m,則儀器的i角為()

A.21.4″
B.-21.4″
C.20.6″
D.-20.6″

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