A recent study found that snoring, though not common in either group, is more common among smokers than among nonsmok...

Skylar on April 12 at 08:38PM

@emilydemmer, happy to help!

(A) is correct because it introduces an alternate cause for both snoring and smoking, which suggests that the passage confused correlation with causation.

Does that make sense? Please let us know if you have any additional questions!