Which choice most logically completes the text?

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Plants often reduce photosynthesis in undamaged parts of their leaves when other parts are being eaten by insects. It appears that feeding triggers the closure of stomata-tiny openings that allow carbon dioxide to enter the leaf-thereby limiting plants' ability to fix carbon (capture and convert it to carbohydrates during photosynthesis). In a study of genetically identical plants, those that were modified to emit an insect-deterring chemical compound experienced a smaller decline in photosynthesis under insect attack than those that did not emit the compound. Since the two types of plants showed no other differences, this finding suggests that ______

emitting the defensive compound enabled plants to keep their stomata open to a greater extent than they otherwise would have.

plants that emitted the defensive compound converted a greater proportion of captured carbon to carbohydrates than they otherwise would have.

emitting the defensive compound allowed plants to compensate for stomata closure by fixing carbon more efficiently.

there may have been underlying genetic differences between the plants that strengthened the correlation between compound emission and photosynthesis efficiency.