GMAT Critical Reasoning (CR) | Several gastrointestinal illnesses are contracted by swimming

Good Question.

Which of the following supports the authorities'decision?
Question Type : Assumption. We need to find the missinginfo.
Conclusion : The authorities have decided to invest money in tests which reveal the existence of non-infectious bacteria.

The "non-infectious" bacteria is mentioned only in the conclusion. So, adding any new info about it will be the assumption.
Only A and B have "non-infectious" bacteria as the subject. B wins.
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