A – Wrong
The passage does not suggest this in any way. Therefore, this cannot be a flaw.
B – Correct
Since musicians undertake music training, their brains may develop the tendency to synchronise to different types of music. Hence, they are more able to synchronise to slow music than non-musicians.
C – Wrong
This is the easiest option to eliminate. The passage does not suggest that non-musicians may undertake musical training in the future. This is not a flaw.
D – Wrong
Although this statement may be true by itself, the passage only focuses on synchronisation to slow music. It does not discuss any different ability of a musician. Therefore, this statement is irrelevant to the question.