sentences: wheels are a part of roller skates & a roller skate is a kind of vehicle ->  a roller skate is a kind of vehicle with wheels  a roller skate is a kind of vehicle with wheels & a wheeled vehicle is a kind of vehicle with wheels ->  a roller skate is a kind of wheeled vehicle  a roller skate is a kind of wheeled vehicle & a wheeled vehicle requires smooth surfaces ->  a roller skate requires smooth surfaces  blacktop is made of asphalt concrete & asphalt has a smooth surface ->  a blacktop has a smooth surface  a roller skate requires smooth surfaces & a blacktop has a smooth surface -> a roller skate can be used on a blacktop surface