Critical Reasoning

In 1980, Country A had a per capita gross domestic product (GDP) that was $5,000 higher than that of the European Economic Community. By 1990, the difference, when adjusted for inflation, had increased to $6,000. Since a rising per capita GDP indicates a rising average standard of living, the average standard of living in Country A must have risen between 1980 and 1990.
Which one of the following is an assumption on which the argument depends?
(A) Between 1980 and 1990, Country A and the European Economic Community experienced the same percentage increase in population.
(B) Between 1980 and 1990 the average standard of living in the European Economic Community fell.
(C) Some member countries of the European Economic Community had, during the 1980s, a higher average standard of living than Country A.
(D) The per capita GDP of the European Economic Community was not lower by more that $1,000 in 1990 than it had been in 1980.
(E) In 1990, no member country of the European Economic Community had a per capita GDP higher than that of Country A.

I have no clue why D is the answer. The explanation in the Bible seems to be too convoluted.

Plz help!!