Which of the Following Scenarios Exemplifies a Dose-Response Relationship

Which of the following scenarios exemplifies a dose-response relationship?

A) When a person is exposed to a toxicant at any dose, there is a negative response.
B) Once exposure to a toxicant reaches a specific level, there is a negative response.
C) The response to a toxicant exposure can be affected by the level of a specific gene's expression.
D) As the concentration of a toxicant exposure increases, the negative response increases.