Passage Summary: Some economists act like their country is an island, but since international trade affects everything, the author says they have to look at the global picture if they want the economy to do well.

Conclusion: Government economists must account for international factors if they want their countries to achieve economic success.

Reasoning: Economies are open systems where global trade impacts internal wages and prices, similar to how physics had to move beyond idealized, frictionless models to be accurate.

Analysis: This is a Sufficient Assumption question, so we are looking for a 'bridge' that makes the conclusion logically inescapable. The premises establish that economies are open systems and that trade has significant effects, but the conclusion introduces a new requirement: the 'must' of looking beyond borders for 'prosperity.' We need an assumption that connects the nature of open systems to the necessity of global analysis for the specific goal of prosperity. Look for a conditional statement that says if an economy is an open system, then its economists must look beyond national borders to ensure it prospers.