问题详情

What proved that nearly half of the author’s professional career was a mistake ？
A)Few of the participants in his training programs made great achievements.
B)Few of the participants in his training programs graduated from the courses.
C)The author made inaccurate assumptions about how to increase student achievement.
D)The author came to the wrong conclusions about how to increase student achievement.请帮忙给出正确答案和分析，谢谢！