A passage about climate policy states: 'Countries that signed the agreement saw emissions fall by an average of 18%.' Which of the following additional facts would most strengthen the claim that the agreement caused the reduction?
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A
The agreement was signed by 50 countries
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B
Countries that did not sign the agreement saw no significant change in emissions over the same period
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C
The agreement was praised by environmental groups
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D
Emissions fell in at least one country that signed the agreement