Choice "C" is correct. Expenses are necessarily incurred to generate revenues. All expenses incurred to generate a particular revenue should be recorded in the same period in which the revenue is recorded.
Choice "b" is incorrect. Losses are never "matched" against gains.
Choice "a" is incorrect. Revenues are not matched to expenses; expenses are matched to the revenues they generate.
Choice "d" is incorrect. Gains and losses are not "matched."
