Final answer:
The most significant economic justification for tariffs is the a) protection of infant industries by providing temporary support and protection from foreign competition.
Step-by-step explanation:
The argument in favor of tariffs that has enjoyed the most significant economic justification is a) Protection of infant industries.
The infant industry argument for protectionism suggests that small domestic industries need to be temporarily nurtured and protected from foreign competition until they become strong competitors.
This approach has been used successfully in some cases, notably in East Asia.
By providing temporary protection to new industries, countries can promote their growth and competitiveness in the global market.