According to the passage, what material is required for lithography

A．During its whole history it sold 7,000 prints.
B．The firm's prints were especially popular in Europe.
C．The average number of prints from each picture was fewer than 7,000.
D．Street vendors were among the firm's most effective sale forc

A．explain that self-control is the key to success
B．teach people how to control everything in order to make a great success
C．distinguish all kinds of self-control and suggest ways for it
D．advise people not to lose temper so as to make and keep more friends