Final answer:
The imposition of standards as nontariff barriers is exemplified by Japan's refusal to import light mayonnaise containing potassium sorbate and Canada's categorization of orange juice with added calcium as a drug subject to special requirements.
Step-by-step explanation:
Nontariff barriers are a way for a country to establish rules, regulations, and inspections to make it more difficult or costly to import products. They can include safety standards, rules-of-origin regulations, and other measures. Examples of the imposition of standards as nontariff barriers include Japan's refusal to import light mayonnaise with potassium sorbate and Canada's categorization of orange juice with added calcium as a drug subject to special requirements. Therefore, options A and B are examples of the imposition of standards as nontariff barriers.