Passage Summary: Some people have bad-looking spinal disks but feel fine, so the doctor claims those disks can't be the reason other people are hurting.

Conclusion: Bulging or slipped disks cannot be the cause of serious back pain in patients who suffer from it.

Reasoning: A study of individuals who reported no back pain revealed that half of them actually had bulging or slipped disks.

Analysis: The doctor is making a classic LSAT error by assuming that because a condition is not a sufficient cause of pain (it doesn't happen to everyone), it cannot be a necessary or contributing cause for anyone. It’s a bit like saying that because some people can walk through a field of pollen without sneezing, pollen can't possibly be the cause of anyone else's hay fever. The argument fails to consider that the same physical condition might affect different people in vastly different ways. Look for an answer that highlights this failure to account for individual variation in symptomatic responses.