单项选择题
A. ways to develop economy B. systems of rewarding students C. approaches to solving problems D. methods of improving performance
A．They have no doubts about them. B．They have doubts about them. C．They approve of them. D．They avoid talking about them.
A．Assigning them tasks they have not dealt with before. B．Assigning them tasks which require inventiveness. C．Giving them rewards they really deserve. D．Giving them rewards they anticipat