A. File-sharing networks carry a more complete variety of music than most traditional music stores.
This
doesn't explain why file-sharing networks will lead to more CDs purchase.
B. The few people using file-sharing networks already purchased more music than most people.
This
doesn't explain the reason behind file-sharing networks leading to increase in CDs purchase, this option just gives us an info on distribution of people using file-sharing networks. We are more interested in knowing the reason.
C. Many people prefer to store their music as computer files rather than maintain large CD collections.
This
doesn't explain, rather this deepens the paradox, why CDs purchase would increase if many people prefer storing their music on computer files.
D. Many consumers have purchased music by artists they discovered through file-sharing networks.
This
explains, this link presents us a
cause effect relationship. Think like I discovered a good music composition through file-sharing network and later I went to a shop to purchase CD for that music.
Another analogy: I saw an advertisement of a product on TV and went to a shop to buy that product. Thus, TV ads causing an increase in the product sales.
E. Music available on file-sharing networks is of the same audio quality as music on commercially produced CDs.
This
doesn't explain, rather this deepens the paradox, why CDs purchase would increase if audio quality of music available on both platforms is same.