Which response is known as an all-or-none response?

• A. Graded
• B. Quantal
• C. Partial
• D. Dose-limited

Answer: (B)

All-or-none outcomes are described by a quantal dose–response relationship. In this approach, each individual either shows the defined effect or does not at a given dose, so the magnitude within a single subject is binary rather than graded. As dose increases, more individuals reach the threshold to respond, so the fraction of responders in the population rises, yielding an S-shaped curve when you plot the percentage of responders versus dose. This contrasts with a graded response, where the magnitude of effect in an individual increases smoothly with dose. Partial and dose-limited are not standard terms that capture the all-or-none, binary nature of whether the response occurs at all in individuals.