Answer:
D) the inflation differential.
Step-by-step explanation:
The inflation differential is simply the different inflation rates between two different countries. Usually an increase in the foreign exchange price of a currency (the currency depreciates) will lead to higher domestic inflation, since one of the reasons why the currency might have depreciated on the first place was a high inflation rate.
When the foreign exchange rate increases, domestic goods become cheaper while imported goods get more expensive, which actually increases the purchasing power of foreign currencies. In this case, the purchasing power parity of the dollar (the base unit) increases against the domestic currency.