Dominic has contracted HIV. What was MOST likely the cause of this virus?

He inhaled droplets from a close friend's sneeze.
He didn't thoroughly wash his hands after using the restroom.
He shared a dirty needle when injecting drugs with a friend.
He consumed food that wasn't cooked to a safe temperature.

The most likely cause of HIV transmission in this scenario is sharing a dirty needle when injecting drugs with a friend. HIV is primarily transmitted through certain body fluids, including blood, semen, l fluids, and breast milk. Sharing needles or other drug injection equipment with an infected person can greatly increase the risk of contracting HIV. The other options mentioned (inhaling droplets from a sneeze, not washing hands, consuming undercooked food) are not common modes of HIV transmission.