Choice "C" is correct. Foreign currencies are like anything else: their value can go up or down. If the dollar price of the euro rises, then the euro is getting more expensive. That means that the dollar is getting less expensive. Another way to say the same thing is that the dollar is depreciating against the euro.
Choice "a" is incorrect. This choice is backwards.
Choice "d" is incorrect. The euro is the currency of Europe (or at least a large portion of Europe). If the price of the euro increases relative to the U.S. dollar, it will not buy fewer European goods. When the price of the euro rises, the price of European goods will also increase, and the euro will buy the same amount of European goods, but more U.S. goods.Choice "b" is incorrect. When the price of the euro rises, the euro will buy more, not fewer, U.S. goods.