What is the primary mechanism of action of diphenhydramine hydrochloride, and for what conditions is it typically prescribed?
a) Diphenhydramine HCl primarily acts as a beta-agonist and is used to treat chronic obstructive pulmonary disease (COPD)
b) Diphenhydramine HCl functions as an H1-antihistamine and is commonly prescribed for allergy relief and as a sleep aid
c) Diphenhydramine HCl inhibits acetylcholine receptors and is used for managing Parkinson's disease
d) Diphenhydramine HCl acts as a selective serotonin reuptake inhibitor and is prescribed for major depressive disorder