A) because the United States was providing aid to Israel
During the Arab-Israeli war, Israel was at war with the nations surrounding her (the Arab nations). These specific nations provided the US with large quantities of oil. However, with the loss of support from the US (as the US supported Israel), the Arab nations cut off supplies of oil to the US, leading to a large oil shortage and the US researching for new ways to make oil, which led to the creation of synthetic oil.
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