15. Concerning β-adrenergic agonists as used in the treatment of asthma, which of the following statements are TRUE? ( a ). The mechanism of action is through activation of adenyl-cyclase, increasing intracellular c-AMP. (b) Oral delivery of β-adrenergic agonists has a similar side effect profile to that of aerosol delivery. (c). Tachycardia due to selective β-2 agonists may be due to “crossover” with β-1 stimulation as well as a reflex response to peripheral vasodilatation. (d). Breath activated powder inhalers require more patient coordination than metered dose inhalers. (A) (a) + (b) (B) (a) + (c) (C) (a) + (b) + (d) (D) (b) + (c) + (d)