The author of the passage is probably a ______. ( )

A．It is good to correct all the errors
B．A teacher should write something on the papers to encourage his students
C．A teacher’s handwriting must be tidy and clear
D．A teacher had better point out the way for each student to improve his writing

A．To describe some successful doctors
B．To compare poor writers with diseased people
C．To tell the teachers why some students are poor in health
D．To show the importance of a teacher’s job