Researcher: Any country can determine which type of public school system will work best for it by investigating the public school systems of other countries. Nationwide tests could be given in each country and other countries could has the best scores on these tests.
What this question is testing
Your task
Find the assumption the argument requires in order for its conclusion to hold.
Common trap
Answers that would help the argument but aren't strictly required (sufficient, not necessary).
Winning move
Negate each choice — the right one breaks the argument when negated.
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