Which item could potentially carry a foreign animal disease into the United States?

The rationale behind identifying a salted dried ham sandwich as a potential carrier of foreign animal disease lies in the inherent nature of animal products. Meat products, like ham, can harbor pathogens that pose a risk to animal health, including those that are not visible and can survive in processed foods. In many countries, certain meat products are not allowed to be imported due to their potential to introduce diseases such as swine fever or foot-and-mouth disease.

While water and fruit can also carry risks, their contexts differ significantly from animal products. A sealed bottle of water is usually processed to eliminate contaminants that could carry diseases, and even when unsealed, fruit varies in its risk depending on the species and country of origin, but it generally does not host diseases in the same manner that meat products do. Books, on the other hand, are not typically involved in the transmission of animal diseases since they do not contain organic material conducive to harboring pathogens. Thus, among the choices, the salted dried ham sandwich stands out as the most likely candidate for introducing foreign animal diseases into the U.S.