This question asks you to draw an inference from information in the last paragraph of the passage. The best answer is C. According to the passage, the Geminid meteor shower occurs yearly; because meteor showers occur whenever the Earth passes through a meteor stream, one can infer that the Earth crosses the Geminid stream once every year. Choice A is incorrect because the passage provides no information from which to generalize about the age of meteor streams. Choice B, which is directly contradicted by the passage, is also incorrect. Choice D is incorrect. The passage says that the Earth would take just over a day to cross the stream if the stream were 5,000 years old. However, in the next few lines the passage states that in fact an average of only 19 hours elapsed between the time that the Earth entered the stream until the time that it exited, leading researchers to conclude that the stream is only about 3,000 years old.