If we assume people can only be influenced by the loudest thing they’re listening to, (A) is right. No assumptions allowed, though, and that’s a silly assumption anyway.

(B) would be more tempting if it were worded much more weakly. Like “backwards messages can be added while still preserving at least some of the qualities…”

But in a world where subliminal messaging sometimes happens, adding the messaging in could have a teeny tiny minor effect on the musical quality and still be effective.

(C) presents a plausible hypothesis about what kinds of recordings work best. Like “ooohhh I bet they pick meditative ambient music!”

This is an Inference question, though. Good guesses =/= supported inferences.

The “if” clause here is excellent – it allows (D) to reach a lot farther than the other answers while still being supported.

The stimulus gives us a single premise, which is pretty hard to work with. (D) essentially says “Nice premise! If we could add this other one onto it, we’d get an actual conclusion!” Here’s a breakdown:

P1: Some recordings influence people via backward messages.
P2: Influence requires comprehension.
________
Con: People can comprehend backward messages.

The stimulus gives us P1. (D) doesn’t assume P2 is true – it says if P2 were true, the conclusion would follow.

See (A) and (E) for good counterexamples. Both answer choices could be repaired by building in an “if” statement that incorporates the assumption they make.

(E) follows if we assume being influenced by music requires paying full attention. But this is an Inference question! No assumptions allowed!