B

Subfornical organ, area postrema and neurohypophysis are all circumventricular organs whose capillaries are fenestrated and devoid of a classical blood-brain barrier [McKinley 2003, PMID 12901335; Morita 2012, PMID 22584508]. The habenular trigone is not a circumventricular organ and retains an intact barrier, so it is the exception.