Critical Reasoning (CR) | Scientists have shown that older bees

Scientists have shown that older bees, which usually forage outside the hive for food, tend to have larger brains than do younger bees, which usually do not forage but instead remain in the hive to tend to newly hatched bees. Since foraging requires greater cognitive ability than does tending to newly hatched bees, it appears that foraging leads to the increased brain size of older bees.

Which one of the following, if true, most seriously weakens the argument above?

(A) Bees that have foraged
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