Concept:
A trade barrier is a government-imposed restriction on international trade. Governments use trade barriers such as tariffs, quotas, and regulations to control the flow of goods and services between countries.
Step 1: Understand the meaning of trade barriers.
Trade barriers are measures taken by governments to regulate imports and exports. They help protect domestic industries from excessive foreign competition.
Step 2: Analyze the given options.
- Promoting foreign companies is not the aim of trade barriers.
- Controlling domestic production is not their main purpose.
- Regulating foreign trade entering the country is the main objective.
- Trade barriers do not completely stop foreign trade.
Step 3: Identify the correct option.
Therefore, the main purpose of trade barriers is:
\[
To regulate foreign trade into the country
\]
Hence, the correct answer is
Option (C).