A.4~5個(gè)立桿間距或5~7m B.6~8個(gè)立桿間距或7~9m C.8~10個(gè)立桿間距或8~10m D.2~4個(gè)立桿間距或2~4m
A.200mm B.250mm C.300mm D.350mm
A.h+1.5a B.h+2a C.h+2.5a D.h+3.0a