Of those person who became teachers in 1968 and who later left the pro

I'm of the same opinion, the conclusion falls apart on negating C and same cannot be seen wrt B

[b]GMATNinja if you could share your views on the same

Answer choices C, D, and E are out of scope. The prompt gives no information regarding why a group of teachers left the profession, qualities of people who continue to teach, and the capabilities of people who left the profession.

Hence, it boils down to A and B.

Choice A: only talk about one group cited in the prompt which asks about persons. Hence, the correct answer choice should address all the groups.

Choice B:
1) addresses all the groups from the prompt
2) if this does not hold then the conclusion breaks. If the two groups cannot be compared with each other on the basis of factors that determine their salaries, then the conclusion loses its validity.

Answer: B

Can you kindly explain why B is the correct answer?
thank you

This argument concludes the figures "indicate how underpaid teachers are today." How do the figures support this idea?

Well, the argument compares two groups -- those who stayed in the teaching profession, and those who left. The argument then notes that twice as many people in the "left-teaching" group compared to the "stayed-in-teaching" group earn more than $35,000. According to the argument, this demonstrates that teachers are underpaid.

So is (B) a required assumption for this argument?

Well, the argument is based on the idea that teachers are getting paid less than they would if they left the profession. In other words, the argument assumes that the teachers who stayed in the profession COULD be making more if they left. But how do we know that's true?

What if the teachers who stayed in the profession would NOT make more money if they left? What if the people who left teaching are getting paid more because they have different skills? Skills that allow them to make more money outside the teaching profession? If that were the case, the figures wouldn't support the idea that teachers are underpaid.

So as (B) says, to reach its conclusion, this argument assumes that the people who left teaching and those who stayed are incomparable in terms of how much money they'd make outside the teaching profession. Because if they weren't comparable, we couldn't really be sure that the teachers are being underpaid.

I hope that helps!