sentences: metal is a kind of natural resource & aluminum is a kind of metal -> tin is a mean of artificial ball aluminum is a kind of natural resource  aluminum is a kind of natural resource & tin frosting are made of tin -> aluminum cans are made of a natural resource aluminum cans are made of a natural resource  tin values are made of a artificial scientists & recycling resources has a positive impact on the conservation of those resources -> recycling aluminum cans has a positive impact on the conservation of those resources