Answer:
B) the current exchange rate on the date of preparation of the financial statement.
Explanation:
All foreign asset accounts have to be translated at current rates. This means that they have to use the exchange rate that was valid during the time the financial statements were being prepared.
This same rule applies to anyone that has gone on vacations to a foreign country. When you come back you exchange whatever foreign money you have left to US dollars and this will be done using that day's valid exchange rate.