Final answer:
Voluntary export restraints (VERs) are a form of specific limitations on trade as they impose a quantity control on exports.
Step-by-step explanation:
Among the options presented, voluntary export restraints (VERs) represent a type of nontariff barrier that strictly falls under the category of specific limitations on trade. Voluntary export restraints are a form of trade restriction on the volume of exports negotiated by the exporting country with the importing country. This limitation can be as effective as traditional quotas in restricting the supply and affecting the price levels of imported goods.
Other options listed such as import credit discriminations, export subsidies, embargoes, and packaging, labeling, or marking standards are also forms of nontariff barriers, but they are not specifically about limitations on the quantity of trade. Instead, they are intended to either encourage domestic production, penalize specific goods, or ensure that importation meets certain criteria which do not necessarily limit the volume of trade directly as VERs do.