focused
v.v. to give all your attention or effort to one particular thing. You use this when you want to ignore distractions and finish a task.
v. to concentrate one's attention or effort on a specific activity, subject, or problem. Transitive when used with a direct object; frequently used intransitively with the preposition 'on'.
She focused on her homework until it was finished.
The marketing team focused their efforts on social media to reach a younger audience this year.
While the initial report touched on several minor issues, the subsequent investigation focused exclusively on the systemic failures that led to the structural collapse.
When used intransitively, it almost always takes the preposition 'on'.
we must focus in the problemwe must focus on the problemLearners often use 'in' or 'at' due to native language interference, but 'focus' requires the preposition 'on'.