Ancient Theories of International Economics from the 18th and 19th

Ancient theories of international economics from the 18th and 19th Centuries are

A) not relevant to current policy analysis.
B) are only of moderate relevance in today's modern international economy.
C) are highly relevant in today's modern international economy.
D) are the only theories that actually relevant to modern international economy.
E) are not well understood by modern mathematically oriented theorists.