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Critical Reasoning: Conclusion Weakening Questions

Fish breeder: A rare illness known as Smith-Kreal disease is spreading continuously and has already killed 19% of our fish. I recommend that we drain and refill the ponds while executing some form of isolation operation.

Exporter: That would not help. We should feed the fish with increased doses of vitamins to strengthen their immune systems against any viral attack.

Which of the following, if true, most weakens the exporter's suggestion?

Incorrect.

[[snippet]]

This answer choice weakens the breeder's recommendation by stating that carrying out his plan may kill many of the fish. This indirectly strengthens the exporter's suggestion, but you should be looking for a statement that weakens it.

Incorrect.

[[snippet]]

This answer choice directly strengthens the exporter's suggestion, but you were supposed to weaken it. If disease can be prevented by medication, then the exporter's suggestion to give the fish vitamins makes sense. 

Incorrect.

[[snippet]]

This answer choice neither weakens nor strengthens the exporter's suggestion. The fact that the disease is restricted to genetically engineered fish is irrelevant. We are already told that the disease is affecting some of the fish in this case. Our task is to find a statement that can weaken the exporter's suggestion about how to deal with the disease.

Incorrect.

[[snippet]]

This answer choice neither weakens nor strengthens the exporter's suggestion. The exporter promotes the vitamins as an alternative to draining the ponds, not as a means to help the fish survive the process. Therefore, the fact vitamins are inefficient in this sense is irrelevant.

Superb!

[[snippet]]

This answer choice weakens the exporter's suggestion to use vitamins. It does so by stating that once the fish have contracted the disease, they are powerless against it, regardless of the form or level of biological defense they may have. This means that even a strong immune system is no match for the Smith-Kreal virus. Therefore, the exporter's suggestion is impractical.

The Smith-Kreal disease, first identified and investigated by Erwin Smith and Jason Kreal, is so violent that it can overpower any form or level of biological defense a fish may have.
The drainage of a fish-breeding pond can be a stressful event that can result in the unnecessary death of many fish.
Diseases in fish can be prevented by strengthening the animals through appropriate medication or dietary manipulation.
Because it can only be contracted by genetically engineered fish, the Smith-Kreal disease was only discovered in 1994.
While vitamin supplements improve general health of fish in ponds, they have been found to be inefficient in helping fish withstand the shock of pond drainage and transfer.