Which Statement Best Describes the Concept of Realization as It

Which statement best describes the concept of realization as it applies to gain or loss?

A) Realization is the recording of gain or loss on a tax return.
B) Realization is the result of an exchange of property rights in a transaction.
C) Realization is the excess of amount realized over adjusted basis.
D) Realization is the excess of adjusted basis over amount realized.