Every year, migratory monarch butterflies travel thousands of miles from Canada to a small forest in Mexico. Scientists have observed that when milkweed plants disappear along the migration route, the butterfly population at the Mexican forest decreases significantly. Question: What conclusion is most supported?
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A
Milkweed availability along the migration route is critical to monarch butterfly survival.
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B
Monarch butterflies are finding a shorter route to Mexico.
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C
The Mexican forest is growing too small to support the butterflies.
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D
Butterflies prefer Canada's climate to Mexico's.