英文關鍵字
built
cement
cleaning
concrete
conservation
dirty
environment
environmental
factory
flowing
industry
made
man
outdoors
pipe
plant
pollution
purified
purity
sewage
sewer
structure
technology
treatment
water
英文關鍵字
built
cement
cleaning
concrete
conservation
dirty
environment
environmental
factory
flowing
industry
made
man
outdoors
pipe
plant
pollution
purified
purity
sewage
sewer
structure
technology
treatment
water