Final answer:
Between Thursday and Friday, the U.S. dollar depreciated against the euro, and concurrently, the euro appreciated against the U.S. dollar. Therefore, options B and C are both correct responses to the exchange rate changes.
Step-by-step explanation:
The question asked is related to changes in exchange rates and their impact on the value of currencies. On Thursday, the exchange rate was 1 USD to 0.50 euros, which changed to 1 USD to 2.10 euros on Friday. This indicates that for the same amount of USD, you would receive more euros on Friday than on Thursday. Therefore, the correct answer to what happened between Thursday and Friday is that the U.S. dollar depreciated against the euro, and the euro appreciated against the U.S. dollar. Hence, both answers B and C are correct.
An exchange rate is the value of one currency for conversion to another. When the exchange rate moves in such a way that a currency strengthens, you get more of the foreign currency per unit of your currency, meaning your currency has appreciated. Conversely, when you get less of the foreign currency for your currency, it means that your currency has depreciated. In this question, where the amount of euros you get for 1 USD has increased significantly from 0.50 euros to 2.10 euros, the U.S. dollar has weakened or depreciated relative to the euro, while the euro has become stronger or appreciated relative to the U.S. dollar. This shift can have an impact on international trade, as seen in historical examples where a stronger euro can discourage exports from European firms to the United States, as the cost of production in euros becomes higher compared to the sales revenues in U.S. dollars.