单项选择题
A.pleasant B.hard C.good D.bad
A. Psychologists do not yet know how people see. B. The best experiments are those in which all factors are controlled. C. The study of perception is going on now. D. Perception does not involve psychological factors.
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