单元：Unit 13.txt

• litter
• bottom
• fisherman
• coal
• public
• ugly
• advantage
• cost
• wooden
• plastic
• make a difference
• shark
• fin
• cut off
• method
• cruel
• harmful
• chain
• ecosystem
• low
• industry
• law
• reusable
• afford
• transportation
• recycle
• napkin
• gate
• bottle
• president
• inspiration
• metal
• creativity