Option 1 -> Defiant means showing resistance or disobedience, unrelated to wordiness or brevity.
Option 2 -> Silent means making no sound, but isn't the direct opposite of being wordy.
Option 3 -> Loquacious means talkative or wordy, which is similar to prolix, not opposite.
Option 4 -> Succinct means brief and concise, the direct opposite of prolix which means wordy and lengthy.
Hence, Option 4: Succinct -> Prolix means using excessive words or being tediously lengthy, while succinct means expressing ideas briefly and clearly -> correct