Answer:
A. Countries find it difficult to export their goods to foreign markets.
Explanation:
Tariffs are taxes on foreign goods. They are a form of economic protectionism, and their main purpose is to protect domestic producers from foreign competition.
A the start of the Great Depression, many countries raised tariffs, making it difficult for other countries to export their goods, simply because now they were more expensive due to the tariffs, and as a result, less people could afford them (the demand for them fell).