Choice A is the best answer. The previous question asks, based on Wegner's experiments, when people would be inclined to think of specific information sources. The answer, that being asked to provide facts that aren't already familiar to them provokes this response, is best supported by the second sentence of the fifth paragraph: “In the first experiment, participants demonstrated that they were more likely to think of computer terms like 'Yahoo' or 'Google' after being asked a set of difficult trivia questions."
Choices B, C, and D are incorrect because the cited lines don't support the answer to the previous question. Instead, they describe the different parameters for the participants in the second and third experiments (choice B), summarize the results of the second and third experiments (choice C), and summarize the results of the fourth experiment (choice D).