Which option best describes CAPTCHA?

• A. Biometric authentication.
• B. Two-factor authentication.
• C. Security logs.
• D. CAPTCHA to prevent automated bots from accessing web services by requiring human verification.

Answer: (D)

CAPTCHA is a challenge-response test that helps websites distinguish humans from automated bots. By presenting a task that humans can complete easily but automated programs struggle with—like recognizing distorted characters or selecting specific images—the site verifies a real person is on the other end. This verification helps prevent automated abuse such as spam, credential stuffing, or scraping, making it the best description of CAPTCHA’s purpose. The other options describe different concepts: biometric authentication relies on physical traits, two-factor authentication adds a second authentication factor, and security logs are just records.