水准仪i角检测中,前后视距均为42m测得高差后,移仪器于一尺近旁测得远处尺上读书b′,其与应读前视b之差b′-b=-6mm,则此仪器的i角为( )。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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