Answer:
c
Step-by-step explanation:
The goal is to restrict Nation's A's access to weapons-making materials. Having a free trade zone with them would decrease the price and make it easier for them to import it. Placing tariffs and quotas only limit the number of imports or make it more costly.
The most effective way to achieve the goal is thus to place an embargo on the trade of certain items with Nation A. This would ban the export of certain goods from the US to Nation A.