Explanation

A credit loss occurs when a counterparty defaults and you have a positive replacement cost - meaning you would have to pay more to replace the contract in the current market.

Option A: ✓ Correct

• You are short Euros (meaning you have agreed to sell Euros at a fixed rate)
• Euro has appreciated (meaning the current spot rate is higher than your contract rate)
• If counterparty defaults, you lose the opportunity to sell Euros at the favorable contract rate
• You would have to replace the contract at the current higher Euro rate, resulting in a loss

Option B: ✗ Incorrect

• You are short Euros
• Euro has depreciated (current rate is lower than contract rate)
• If counterparty defaults, you can replace the contract at a more favorable rate
• No credit loss - actually beneficial to you

Option C: ✗ Incorrect

• You sold a call option (you are the writer)
• Euro has appreciated
• As the option writer, you have already received the premium
• If counterparty defaults, you keep the premium and are relieved of the obligation
• No credit loss

Option D: ✗ Incorrect

• You sold a call option
• Euro has depreciated
• The option is likely out-of-the-money and won't be exercised
• If counterparty defaults, no loss occurs

Therefore, only Option A represents a situation where counterparty default would cause a credit loss.