Beta blocker with d isomer responsible for beta blocker action is ?

Ans. is 'a' i.e., Nebivolol Nebivolol is a novel betal-blocker with a greater degree of selectivity for betal-adrenergic receptors than other agents in this class and a nitric oxide (NO)-potentiating, vasodilatory effect that is unique among beta-blockers currently available to clinicians. Nebivolol is a racemic mixture with beta-blocker activity residing in the d-isomer; in contrast, I-nebivolol is far more potent in facilitating NO release. Note : Beta blockers with 1 isomer having beta blocking activity are :? Propranolol, atenolol, metoprolol, esmolol, timolol