Final answer:
In QBO Plus, entering a purchase order for stock does not affect any accounts because purchase orders are considered non-posting transactions.
Step-by-step explanation:
When entering a purchase order in QBO Plus, it's important to note that purchase orders are non-posting transactions. This means that they do not immediately affect the financial statements or any accounts in the company's accounting system. Therefore, the correct answer to the question of which accounts are affected by entering a purchase order for stock in QBO Plus is d. None, because purchase orders are non-posting transactions.