单项选择题
A.120 B.150 C.160 D.180
A.露天处所的烟囱 B.旋转机房 C.桅杆、起重柱 D.通风筒
A.300mm B.500mm C.400mm
A.20m;30m B.30m;20m C.30m;40m D.40m;30m
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