In terms of prohibited items, which of the following is considered a violation of U.S. customs regulations?

Lotteries are considered a violation of U.S. customs regulations because the importation of lottery tickets and related paraphernalia is prohibited. This is primarily due to federal laws aimed at regulating gambling activities and preventing illegal gambling activities from occurring within the U.S. These laws prohibit the importation of items that could be associated with lotteries, which often includes various forms of gambling tickets and promotional materials.

In contrast, the other options—electronics, automobiles, and medical devices—are generally permissible for importation, provided they comply with federal regulations and standards applicable to their specific categories. For instance, electronics must meet safety regulations, and automobiles must comply with environmental and safety standards, while medical devices require approval from the Food and Drug Administration (FDA). However, none are inherently prohibited the way lottery tickets are under customs regulations.