Sleeping pills had been showing up with regularity as a factor in

The sentence incorrectly uses the past perfect verb phrase "had been showing up." The past perfect is only used when a sentence involves two past events; the past perfect tense ("had . . .") is used for the earlier past event while the simple past tense is used for the later past event. However, in this sentence there is no second event that takes place in the past. Therefore, the past perfect cannot be used.

(A) This choice is incorrect as it repeats the original sentence.

(B) This choice incorrectly uses the past perfect verb phrase "had been showing up." The past perfect is only used when a sentence involves two past events; the past perfect tense ("had . . .") is used for the earlier past event while the simple past tense is used for the later past event. However, since, in this sentence, there is no second event that takes place in the past, the past perfect cannot be used. In addition, this choice uses the phrase "as factors in traffic arrests." The plural "factors" is incorrect since "sleeping pills" represent only one factor in traffic arrests.

(C) CORRECT. This choice correctly uses the present perfect tense "have been showing up" to indicate an event that started in the past and continues into the present. This choice also correctly uses the phrase "as a factor" rather than "as factors" because sleeping pills constitute only one factor in arrests.

(D) This choice correctly uses the present perfect tense "have been showing up" to indicate an event that started in the past and continues into the present. However, this choice incorrectly uses the phrase "as factors in traffic arrests." The plural "factors" is incorrect since "sleeping pills" represent only one factor in traffic arrests.

(E) This choice correctly uses the present perfect tense "have been showing up" to indicate an event that started in the past and continues into the present. However, the phrase "sleeping pills have been showing up . . .in traffic arrests" nonsensically suggests that the pills themselves have shown up in traffic arrests. In fact, the pills have shown up as a factor in traffic arrests (while the pills themselves are safely hidden in the driver's stomach).