This question asks what the author says about the purpose of the research described in the first paragraph. The best answer is D. According to the author, the purpose of the computer-modeling experiment was to test the hypothesis that meteor streams broaden with time. Choice A is not correct; although the observational data described in the last paragraph allowed scientists to estimate the age of the Geminid stream, this data was analyzed to confirm a surprising prediction made by the computer model. This analysis was not part of the original experiment. Choice B is also incorrect. Although the experiment yielded a surprising prediction about a particular feature of meteor streams, the purpose of the experiment was to determine whether meteor streams broaden with time, not to identify the various structural features of meteor streams. Choice C is not correct because the experiment was undertaken to test a general hypothesis about meteor streams. It was not undertaken to explore the nature of any particular meteor stream, and the passagenever suggests that the actual meteor streams used in the computer model was “particularly interesting”.