This question's explanation and your answers so far.
次の記述のうち，バイオメトリクス認証の例だけを全て挙げたものはどれか。 a Webページに歪んだ文字の列から成る画像を表示し，読み取った文字列を利用者に入力させることによって，認証を行う。 b キーボードで特定文字列を入力させ，そのときの打鍵の速度やタイミングの変化によって，認証を行う。 c タッチパネルに手書きで氏名を入力させ，そのときの筆跡，筆圧，運筆速度などによって，認証を行う。 d タッチパネルに表示された複数の点をあらかじめ決められた順になぞらせることによって，認証を行う。
“a, b”. b is biometric authentication, but a is a CAPTCHA that has the user read and enter a distorted character string; it is a mechanism for confirming whether the user is a human (that is, not a bot), not biometric information unique to the individual. It is not biometric authentication “only”, so it is wrong.
“a, d”. a is a CAPTCHA, and d is pattern authentication that traces dots in a predetermined order — knowledge-based authentication that uses information known only to the individual. Neither is biometric authentication, so it is wrong.
正解 Biometric authentication identifies a person using biometric information unique to that individual — physical traits such as fingerprints, veins, and irises, or behavioral traits such as signatures, keystrokes, and voiceprints. b uses changes in keystroke speed and timing (keystroke dynamics), and c uses handwriting, pen pressure, and pen-movement speed; both rely on behavioral traits unique to the individual, so they count as behavioral biometrics. Only the combination of b and c lists examples that are solely biometric authentication, so ウ is correct.
“c, d”. c is biometric authentication, but d is pattern authentication that traces dots in a set order — that is, knowledge-based authentication, not biometric information. It does not form a combination that lists biometric authentication “only”, so it is wrong.