Question

the main purpose of this poster is to
explain the reasons why s contracted hiv
share scotts personal story about living with hiv
show that hiv is spreading throughout the population
encourage the public to support the fight against hiv

Explanation:

Posters often aim to raise awareness and encourage action. While sharing a personal story can be part of it, the over - arching goal is usually to inspire public support for a cause. In the context of an HIV - related poster, the most likely main purpose is to rally public support in the fight against HIV rather than just to explain reasons for contraction, share a personal story, or simply show the spread.

Answer:

encourage the public to support the fight against HIV