Final answer:
Unrealized holding gains and losses for debt investments differ based on their classification.
Step-by-step explanation:
Unrealized holding gains and losses for debt investments classified as trading should be reported in the income statement.
Unrealized holding gains and losses for debt investments classified as available-for-sale should be reported in other comprehensive income.
Unrealized holding gains and losses for debt investments classified as held-to-maturity should not be reported until the investment is sold or matures.
Therefore, the correct answer is option 4) All of the above.