英文關鍵字
aeration
agriculture
aquaculture
canal
circular
cleaning
cycle
dirty
ditch
engine
environment
floating
flow
function
increasing
industry
machine
metal
motion
motor
nature
old
outdoor
oxygen
paddle
paddles
pollution
pond
power
processing
purification
quality
roll
rotary
rotating
round
rusty
scatter
slow
source
spinning
splashing
spread
sprinkle
surface
tool
turbine
turning
vintage
water
wheel
working