A.應(yīng)大于30m B.應(yīng)大于40m C.應(yīng)大于45m D.應(yīng)大于60m
A.不應(yīng)少于25m B.不應(yīng)少于35m C.不應(yīng)少于45m D.不應(yīng)少于55m
A.8倍 B.6倍 C.4倍 D.2倍