Question

stress may contribute to tension headaches
a due to an upset stomach and disturbed vision.
b by increasing pain sensitivity in already - sensitive pain pathways.
c by increasing pain sensitivity at any time or pathway.
d as a result of infection or allergic reaction.

Explanation:

Stress contributes to tension headaches by affecting pain pathways. Option A (upset stomach and disturbed vision) is not the main mechanism for stress - related tension headaches. Option C ("at any time or pathway") is too broad and not specific to the relationship between stress and tension headaches. Option D (infection or allergic reaction) is not related to stress - induced tension headaches. Option B correctly describes that stress increases pain sensitivity in already - sensitive pain pathways, which is a valid mechanism for tension headaches.

Answer:

B. by increasing pain sensitivity in already - sensitive pain pathways.