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Critical Reasoning: Conclusion Strengthening Questions

Several gastrointestinal illnesses are contracted by swimming in the sea as a result of infectious bacteria in the water. There are tests which reveal the existence of these bacteria, but they are not reliable. Therefore, the authorities have decided not to invest money in those tests, but rather in tests which reveal the existence of non-infectious bacteria.

Which of the following supports the authorities' decision?

Good job!

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This answer choice confirms the argument's assumption: if the non-infectious bacteria exist close to infectious bacteria, the more reliable non-infectious bacteria tests could provide a good indication to whether infectious bacteria are present.

Incorrect.

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This answer choice neither strengthens nor weakens the authorities' decision, as the location in which non-infectious bacteria were found does not help us decide which test to use.

Incorrect.

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At best, this answer choice indirectly weakens the authorities' decision: if the test is new, its efficiency is yet to be proven. This makes the authorities' decision to invest in this test even less understandable and justified.

Incorrect.

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While this answer choice could possibly be seen as strengthening the authorities' decision, it still provides no clear justification for the decision (if the test is pointless, its efficiency is not a great help). There is an answer choice which strengthens the conclusion more clearly. Remember that the correct answer to a Critical Reasoning question should be as simple and straightforward as possible.

Incorrect.

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This answer choice neither strengthens nor weakens the authorities' decision; it simply adds more information to that given in premise A, without supporting the use of non-infectious bacteria tests.

Non-infectious bacteria were always found close to shore.
Where the non-infectious bacteria are found, the infectious bacteria are also found.
The test which reveals the existence of non-infectious bacteria was developed only recently.
Tests which reveal the existence of non-infectious bacteria take less time and cost less money.
One in every ten people who swims in the sea contracts a gastrointestinal illness as a result of infectious bacteria in the water.