Select the most appropriate one-word substitution for the given group of words.

One who is easily duped or fooled 

Gullible

The most appropriate one-word substitution for "one who is easily duped or fooled" is gullible.

• Naive means lacking experience or knowledge of the world.
• Innocent means not guilty of any crime or offense.
• Gullible means easily persuaded to believe something, especially something false.
• Stern means severe or strict.