Most of the time finding music with C (more so, Last.fm), then acquiring with D.
Normally when I grow to like the artist I've listened to I'd buy their album. Rarely itunes download these days though, I am starting to appreciate hard copies again.
Sometimes though, I have to use D to get what I want.
But I still think the music industry isn't losing out with all the "other means" of acquiring music at all. My whole tastes in music have been acquired by just downloading a shed load of music, then finding what I like.
If I couldn't download, I would just not bother listening to that artist, meaning I would not be a fan, meaning I would not pay to go see them in live, or to buy merch, or to buy their albums.
If I am not buying your stuff, then as an artist you're doing it wrong frankly. But a lot of the time, I just don't have the money but still want to enjoy the music, with the possibility of in the future purchasing the physical media.
I think most of the people who go for route D do what I do, or have no money to purchase the real thing, so without it all the artists would just have less fans and a smaller following, as no one would be able to hear their music. Such as children who download the latest bands then go to see them in concert or something. Frankly I see no trouble at all. A vast amount of people still aquire via legal means like mentioned above, so it ticks me off when people in the music industry moan that "illegal" downloading is affecting them. Be happy you've got fans at all, as without them you'd have nothing, at least you have something.
Gone a bit on a tangent here, but I felt as the subject is there, it has to be said.