题目

   The following table shows some results of a survey （调查）in which 800 Japanese school pupils were asked to give their impressions（印象）of their classroom teachers. The pupils’ impressions were found to differ depending on whether the teacher was new (with less than three years’ experience), middle-standing(ten to twenty years), or veteran（有经验的）（twenty to thirty years）. The numbers in the table show the percentage of the pupils who answered “very satisfied” or “extremely satisfied” for each question item （项目） Question Items New Middle-standin已知sin2α=-sinα，，则tanα=（ ）A．B．C．D．