Demographers doing research

Demographers doing research for an international economics newsletter claim that the average per capita income in the country of Kuptala is substantially lower than that in the country of Bahlton. They also claim, however, that whereas poverty is relatively rare in Kuptala, over half the population of Bahlton lives in extreme poverty. At least one of the demographers’ claims must, therefore, be wrong.
The argument above is most vulnerable to which of the following criticisms?
A. It rejects an empirical claim about the average per capita incomes in the two countries without making any attempt to discredit that claim by offering additional economic evidence.

B. It treats the vague term “poverty” as though it had a precise and universally accepted meaning.

C. It overlooks the possibility that the number of people in the two countries who live in poverty could be the same even though the percentages of the two populations that live in poverty differ markedly.

D. It fails to show that wealth and poverty have the same social significance in Kuptala as in Bahlton.

E. It does not consider the possibility that incomes in Kuptala, unlike those in Bahlton, might all be very close to the country’s average per capita income.

My Ques: What is wrong with option A? How does E answer about poverty concerns.

P.S: Also can you please guide I want to practice CR questions. i am through with OG 16 and half of retired gmat pack. But i have not mastered CR very well. Can you please suggest sources i can do questions from? Also repeating those questions does not help in practice.