ogoluwa

Beginning of period: 0.649 USD/SGD
End of Period: 0.671 USD/SGD
SGD is the Local Currency - and USD is the Parent Presentation Currency.
USD has depreciated, and SGD has appreciated.
Under FIFO method - Oldest items are in COGS, latest items are in Ending Inventory.
If Functional Currency were US Dollar - which is the Presentation Currency - Temporal Method. COGS would be at Historical Rate.
Under FIFO - oldest rate @ 0.649 USD would be used to convert COGS - 1000 SGD (assumed) COGS would convert to 649 USD.
LIFO - Current rate @ 0.671 USD would be used to convert COGS - 1000 SGD (assumed) COGS would convert to 671 USD.
If SGD were the Functional Currency - this would be current rate method. So 0.671 would be used - convert to 671 USD.
For Highest gross profit margin - need lowest COGS - so FIFO @ USD (Choice A) is your answer.