Tricky question, ill break down my thought process for you:
The definition of Errors as per Human Being Pilot = "Actions or inactions by the flight crew that LEAD to deviations from organisational or flight crew intentions or expectations". Human being pilot also goes on to say an error can be a link in a chain of errors.
Sometimes it helps thinking to try and pick the answer that cant be wrong (if that makes sense), so based on that id argue that the out of date maps was the first error in the chain of errors which led to the a/c flying towards cta (also possibly a handling error BUT is DEFINATELY a UAS). So since the a/c flying towards CTA is definately a UAS then the only other answer would be taking the outdated maps (which is a procedural error).
