OFFICIAL EXPLANATION:
The original makes a comparison between car sales in 2004 and this January. However, the comparison is of prepositional phrases, which must be compared using "as," not "like," which is used to compare nouns. ("Like" would be correctly used to compare one year to another, for example, "Like 2004, 2005 was a good year.")
Also, this sentence has an idiomatic error. The idiom “as often as” must be written out and cannot be contracted to “as often.” Finally, the phrasing "car sales to first-time buyers as often as to return customers" is awkward and should be recast.
(A) This choice is incorrect as it repeats the original sentence.
(B) This choice incorrectly uses the comparison term "Like." Also, the idiom “as often” is incorrect; it should be “as often as.”
(C) This sentence uses the correct idiom, "as often as." However, the pronoun “it” does not have an antecedent, as “sales” (as well as "buyers") is plural. Finally, "and it" weakens the syntax and meaning of the first part of the sentence.
(D) CORRECT. This choice clearly compares sales in the two years. The idiom “as often as” is correctly written and is placed in a comparison of actions (i.e., "first-time buyers bought cars") rather than in a comparison of prepositional phrases, which is more awkward.
(E) The idiom “as often” is incorrect; it should be “as often as.”