"Paranoid" refers to being excessively worried or obsessed, often with irrational fears of being harmed or persecuted.
"Obsessed with" is the best synonym, as it implies a persistent and irrational focus on something, which aligns with the meaning of "paranoid."
The other options do not capture the specific, irrational obsession implied by "paranoid." Conclusion:
"Obsessed with" is the closest synonym for "paranoid," reflecting irrational or excessive concern.