问题详情

According to Kellerman, why are there so many unhappy adults in the world？
A．Becanse they are not brighter than others.
B．Becaase they don"t have good education.
C．Because they are not doing the things they are best at.
D．Because they are not duly encouraged in life.请帮忙给出正确答案和分析，谢谢！