The correct answer is A. Sympathomimetics relieve nasal congestion associated with colds and allergies by causing vasoconstriction.
Sympathomimetics are drugs that mimic the effects of the sympathetic nervous system, which is responsible for the body's "fight or flight" response. These drugs work by stimulating the alpha-adrenergic receptors in the blood vessels of the nasal mucosa, causing vasoconstriction or narrowing of the blood vessels. This narrowing of the blood vessels reduces blood flow to the nasal mucosa, which in turn reduces inflammation and swelling, and relieves nasal congestion.
