Question

read the sentence
when i told the doctor of my sinus pain and nasal pressure, she offered me a decongestant.
based on the prefix, de-, what does the word decongestant mean?
a device that causes congestion
a resource that defines congestion
a way to measure congestion
a substance that reduces congestion

Explanation:

The prefix "de -" often means "remove" or "reduce". A decongestant is related to dealing with congestion. Since the doctor offered it for sinus pain and nasal pressure (symptoms related to congestion), it makes sense that it would reduce congestion.

Answer:

a substance that reduces congestion