单项选择题
A.1 B.2 C.3 D.4
A、R≤1000m B、R≤1200m C、R≥1200m D、R=1200~4000m
A、4.0 B、4.5 C、5.0 D、5.5
A.R≤1000m B.R≤1200m C.R≥1200m D.R=1200~4000m
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