need answer with explanation for sage 50 accounting

Regarding a purchase from a foreign vendor, when the exchange rate for a foreign currency increases between a purchase and a payment - a. the difference between the two rates is debited to the linked expense account for tracking exchange rate differences b. the difference between the two rates is debited to the asset or expense account for the purchase c. the difference between the two rates is credited to the linked expense account for tracking exchange rate differences d. the payment amount is set by the exchange rate at the time of the purchase