Big class of city的用法和样例：
- Pele was in a class of his own as a footballer.
- The products have five big classes of motor , coincidence device , moderating machine , the condenser , enameled wire.
- He took the ninth position in his class of forty.
- The pressures of city life forced him to move to the country.
- It's no easy task to take control of a class of young children.