gmat 逻辑至尊难题2

Energy

Of those person who became teachers in 1968 and who later left the profession, 30 percent today earn salaries above $35,000 a year: of those who became teachers in 1968 and have remained in the profession, only 15 percent today earn salaries above $35,000 a year. These figures indicate how underpaid teachers are today.
The argument above depends on which of the following assumptions about the persons for whom statistics are cited?
(A) At least one-third of the group of persons who have remained in teaching would today be earning more than $35,000 a year if they had left teaching.
(B) The group of persons who left teaching and the group who did not are comparable in terms of factors that determine how much people outside the teaching profession are paid.
(C) Most of those persons who left teaching did so entirely because of the low salaries teachers earn.
(D) As a group, those persons who have remained in teaching are abler and more dedicated than the group of persons who left teaching.
(E) The group of persons who left teaching and who today earn more than $35,000 a year were more capable teachers than the group who remained in the profession.
key is b
B怎么解释，好像意思反了

mariezhu

只有离开的和没离开的是同等水平的人时，才能说留下来的人没有象离开的人那样挣大钱是亏了。 （如果是水平最好的人离开了，那么他们挣了更多的钱也就是合理的了）