Yes, A is wrong because the methylation levels are nearly similar in the first promoter. D is wrong because while this is a true statement, the passage doesn't provide any information about this. Same thing with C. So this leaves B as the best answer. This make sense because we are talking about DNA methylation. The CS patients show differences in methylation in some DNA promoters compared to others, so it is feasible that methylation could cause some kind of change in chromatin structure. As for the controls, they have a positive control so to speak, with the machinery generating spermatozoa -> working but due to physical obstruction no sperm is seen in the semen. Sertoli only syndrome is similar to a negative control; ie the machinery isn't working because Sertoli cells are only present, so one would expect no sperm to be present in the semen.