Critical Reasoning (CR) | Re: The optic nerves of identical twins are genetically identical.

This is a causal argument. Since the optic nerve in the blind twin is smaller than that in the twin with normal vision, the argument concludes that damage to the optic nerve is the cause of blindness. To weaken this argument, we need to assert either that there is some other cause, or that the causality is reversed. Answer B asserts that the causality could be reversed: the small size of the optic nerve might be the result of the treatments given to the blind child. Therefore, the correct answer
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