How were the countries of the arabian peninsula able to modernize quickly during the middle of the twentieth century

During the middle of the twentieth century, the Arabian countries flourished economically and they quickly started to change and to modernize. The reason why they were able to do so, and do it so quickly, was that they had the largest reserves of oil and natural gas. The oil especially was bringing in enormous amount of profit to them as it was the most demanded natural resource in the world. Because such enormous amount of money were coming in these countries, they were able to transform themselves very quickly, thus becoming countries where everything was modernized and of the highest standard. One thing that has to be noticed though is that these countries were not producing for themselves, nor did they developed any other industries, but  pretty much everything was and still is imported.

an angle + its complement = 90 degrees

answer; (d) melting of sea ice;