Final answer:
Unrealized profit in inventory could cause Company A's investment account to decrease under IFRS.
Step-by-step explanation:
Under IFRS, a company's investment account can decrease for several reasons. In this case, the factor that could cause Company A's investment account to decrease is unrealized profit in inventory.
Unrealized profit occurs when a company sells goods to another company at a profit, but the goods have not yet been resold to a third party. This profit is not recognized in the company's income statement, but it is recorded in the investment account.
If the value of the unrealized profit decreases, it would result in a decrease in Company A's investment account.