Many People, When They Have a Sinus Headache, Often Use

Many people, when they have a sinus headache, often use decongestant nasal sprays. Why are such sprays useful?

A) They reduce swelling, allowing the sinuses to drain.
B) They reduce the symptoms of sore throat inflammation, which exacerbates the pain.
C) They dry out the breathing passageways in the pharynx, making it easier to breathe.
D) They have a pain-blocking effect in the brain.