Choice B is the best answer. The majority of the passage focuses on the experiment concerning "how much the crowd influences the individual, and whether it can be controlled from outside" (lines 42-44,"This time...outside"). After explaining the experiment and the results it produced, the passage moves on to consider questions raised by the results, such as whether the findings are site specific or "true in general" (lines75-76,"positive...the"), why different findings are observed, and whether companies can "boost their products by manipulating online ratings on a massive scale" (lines 85-86,"Will...scale").
Choice A is incorrect because the passage does not conclude by explaining the practical ways the experiment's findings have been applied but rather by considering questions the findings raise. Choices C and D are incorrect because the passage does not indicate that there were any flaws in the experiment's findings and does not include statements from anyone who disputes the findings.