13. 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.（B）
(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.
这里
(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.、
为什么不对，如果这帮留校的出去后混得还不如在学校里面，说他们underpaid 就没道理了呀。 | 
