Under U$.$S$.$ GAAP, what is the proper treatment of unrealized foreign exchange gains?

A$)$ They should be deferred on the Balance Sheet until cash is received.

B$)$ The principle of conservatism requires that they should never be recognized.

C$)$ They should not be recorded until cash is received and the exchange transaction is completed.

D$)$ They should be recognized in income on the date the exchange rate changes.