<span>In the European history, the Early Middle ages lasted from 5th to the 10th century. The Early Middle Ages was the period where population was declining, majority of which was from the urban centers. The trades were also decreasing, increasing the immigration. From this statement, D, B, A can be cancelled out.
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The main reason why OPEC imposed an oil embargo on the US is because the US supported Israel in its “Yom Kippur War” with Egypt, and OPEC was made up of states that were against Israel, who was fighting the war against Egypt.
