Government statistics show that the real (adjusted for inflation) average income for families has risen over the last five years. Therefore, since this year the Andersen family's income is average for families, the family's real income must have increased over the last five years.
The reasoning in the argument is most vulnerable to criticism on the grounds that the argument
(A)
ambiguously uses the term "average" in two different senses - WRONG. No, no such ambiguity arises, neither does it impacts.
(B) fails to take into
account inflation with respect to the Andersen family's income - WRONG. Inflation would not be specific to a particular family, it's common for all.
(C) overlooks the possibility that
most families' incomes are below average - WRONG. Most families may be below but we are only concerned about Anderson family's income.
(D) fails to consider the possibility that the Andersen family's real income was above average in the recent past - CORRECT. POE helps. But if the income was above average in the past and now just average then real income has decreased in fact.
(E) presumes, without providing justification, that the
government makes no errors in gathering accurate estimates of family income - WRONG. Error or no error it does not matter as it would have been for all the families.
Answer D.