Explanation:

- Complacent is an adjective that describes someone who is self-satisfied and unconcerned by potential dangers or deficiencies, often to a fault.

- Option 1: Concerned -concerned means worried and feeling concern about something.

- Option 2: Satisfied - Satisfied means content or pleased, which is more akin to complacency, thus not an antonym.

- Option 3: Confident - Confident means having trust in one's abilities or qualities, which is different but not an antonym of complacent.

- Option 4: Trusted - Trusted means regarded as reliable or truthful, which doesn't relate to the sense of complacency.

- Correct Answer:1. Concerned. Which is the best antonym from the given options.