The two subjects compared in the passage "E-books or printed books? That's the question" are people who read electronic books and people who read printed books.
The passage reflects on the digital revolution that also impacted reading, showing an increase in e-book sales, which in 2010 was 164%.
These indices demonstrate the change in consumer behavior, who now have the choice of reading a physical book, or an e-book through their smartphones, e-reader or tablet.
Therefore, the correct alternative is the letter c.
Find out more information about digital revolution here:
https://brainly.com/question/10377689