Which of the following is NOT classified as dangerous goods?

Plain paper is classified as non-hazardous and does not pose a risk in terms of safety or potential harm during air transport. The reason it is not considered dangerous goods is that it does not have any characteristics that would make it a safety concern, such as being flammable, corrosive, explosive, or toxic.

On the other hand, dry ice is classified as dangerous goods because it can release carbon dioxide gas when it sublimates, which can displace oxygen in an enclosed space, creating a suffocation hazard. Wheelchair batteries, particularly lithium-ion batteries, can also be classified as dangerous goods due to their potential to overheat and catch fire under certain conditions. Ammunition is considered dangerous because it is explosive and can also pose serious safety risks if not handled properly during transport.

Thus, plain paper stands out as the only item listed that is safe for transport without special regulations or considerations related to hazardous material handling.