The passage gives us two scenarios. Either pick more expensive or more familiar. Since familiarity is the same, he picks based on it being more expensive.
Answer choice E does the exact same thing. The rabbit either doubles back or flees for nearby cover. Since nearby cover is not possible. The rabbit will double back.
The difference with answer choice C is that firstly, it provides a conditional statement using unless which is different than the structure of the passage. And the conclusion is that of "asteroid Y is more eccentric" rather than something about asteroid Y being the only choice or alternative.
I hope this helps. Please let me know if you have any other questions.