D, If you buy two new games, your opportunity cost is the time you could spend talking on the phone.
Explanation Opportunity cost is the value of the next best thing you give up whenever you make a decision. In this case the opportunity cost of buying the two games is the time you could be using the phone.
The correct answer for the question that is being presented above is this one: "Greeks." The people of Europe had been relying on Rome for political and economic stability. After Rome's fall, the people turn to Greeks for guidance and stability.