A.4.Om B.5.Om C.6.Om D.7.Om
A.4-5個立桿間距或5-7m B.6-8個立桿間距或7-9m C.8-10個立桿間距或8-10m D.2—4個立桿間距或2~4m
A.50mm B.100mm C.150mm D.200mm