Concept:The matching concept requires that revenue earned in a period be matched with the expenses incurred to earn it in the same period.
Explanation:The credit sale of ₦18,000 was made during the current accounting year.
So it is revenue earned this year, even though cash has not yet been received.
Therefore, it must be included in the trading account for the year.
The cost of goods sold relating to this credit sale is also charged in the same period.
This treatment is based on when the sale was made, not on when cash was collected.
Thus, the dual aspect, materiality, and money measurement concepts do not govern this treatment.
Answer:C. Matching concept.