The author never suggested that the length of time one forages will cause significant differences in brain size. The hypothesis is simply that engaging in foraging increases brain size. The effects might occur immediately rather than over time; the author never says otherwise.

The author never suggested that the causal impact of foraging on brain size is only temporary. The hypothesis is that foraging increases brain size; that increased brain size might remain even if foraging stops.

The author never suggested that foraging distance will impact brain size. The hypothesis is simply that foraging increases brain size; the kind of foraging or the distances traveled might not matter.

This still indicates that the brains of older bees are larger than the brains of younger bees. The author never suggested that foraging had to create a significant difference in brain size.

This provides evidence that the true cause of larger brains in the older bees is not foraging, but might be age. If foraging were the cause, we’d expect foragers to have larger brains than non-foragers. But (E) shows this isn’t the case.