发两道我想不明白的xdf题

309. of those persons who became teachers in 1968 and who later left the profession. 30% today earn salaries above $35,000 a year, of those who became teachers in 1968 and have remained in the profession, only 15% today earn salaries above $35,000 a year. These figures indicate how underpaid teacher are today.

the argument above depends on which of the following assumptions about the persons for whom statistics are cited?

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

228. left-handed persons suffer more frequently than do right-handed persons from certain immune disorders, such as allergies. left-handers tend to have an advantage over the right-handed majority, however, on tasks controlled by the right hemisphere of the brain, and mathematical reasoning is strongly under the influence of the right hemisphere in most people

C. there are proportionally more left-handers among people whose ability to reason mathematically is above average than there are among people.

真的不懂啊~~~

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