This argument asks us to find a flaw in the argument. Generally a flaw is linked to an assumption, so let's read the argument with an eye to identifying potential logic gaps.
If you read this carefully, you should have noticed the classic correlation causation fallacy going on here. The author assumes that because two activities correlate with increased theta wave function that one such activity (listening to music) can trigger the other correlated activity (enhanced creativity). The author is necessarily assuming that this is a one way street and/or that there isn't some other unidentified causal factor out there.
Answer choice (D) goes to this point. Just because theta waves are correlated with increased creativity doesn't mean that they cause increased creativity!