Final answer:
The Government (D) has the authority to impose trade barriers such as tariffs or quotas. They use these tools to protect domestic industries and to regulate trade based on national economic interests.
Step-by-step explanation:
The entity that can impose a trade barrier such as tariffs or quotas is D) The Government. Governments have the authority to establish and enforce trade policies at a national level, which can either encourage or discourage trade with other nations. For instance, the United States imposes import quotas on products like sugar to protect domestic industries from foreign competition and possible price undercutting. Another key role of the government, specifically the United States Department of Commerce, is to determine if there is import dumping, a practice where foreign producers sell goods in the U.S. at an unfairly low price. If substantial injury to domestic industries is found by the United States International Trade Commission, the president has the power to impose tariffs designed to offset these low prices and protect the national economic interests.