What type of stamps are included in accountable paper items?

The correct answer is that postage stamps are included in accountable paper items. Accountable paper items are those that have a specific value and require tracking due to their potential for loss or misuse. Postage stamps fall into this category because they are used to prepay for postal services and are considered a form of currency, requiring careful management and accountability in handling and distribution.

In contrast, gift cards, while having monetary value, are typically managed under retail and service categories rather than postal services. Promotional stickers and business cards do not hold intrinsic monetary value in the same way and are primarily used for marketing and informational purposes rather than for paying for services. Thus, among the provided options, postage stamps are the only items that are inherently accountable within the postal system.