Just a few thoughts of my own...

Well, here's one perspective on question B that I don't think is often brought up. If it's fair for an adult to be the subject of a porn film, why isn't it for a kid to be the subject? An adult participating would almost certainly know what they were doing, and why (the purpose of the product they were making.) It only seems fair that you would have to explain this to a child as well.

My concern is that the child would have a hard time understanding the "why" without other knowledge of what sex is, why people desire it, etc. If the child was not well educated in this, there is a risk that he or she may gain a perception of sex as a commodity, i.e. a thing to be bought and sold.

I would think it best for children to first understand what one might regard as "precursors" to a positive sexual relationship before engaging in any kind of sex related activities. These precursors would include those of mutual respect, trust, affection, and genuine concern for the well being of a partner. Provided they have all this and some experience to understand what sex actually is, then if they should chose for themselves to engage in making pornography, then I wouldn't take issue with it.

My concern about how CP is likely often produced is that either the kids don't know what they are actually being involved in, that it is disrupting their formation of a healthy understanding of sex, and that they aren't necessarily participating on a voluntary basis.

About question A, I have no idea. It might be a similar argument to the ones about violence on TV or in video games.