Which statement best describes dose-response curves? 

A)  They are extrapolated from humans to other primates. 
B)  They show the effects of various doses of toxic agents on a group of test organisms. 
C)  They are extrapolated using mathematical models to project possible effects of high doses. 
D)  They are linear graphs.

Dose-response curves are graphs that show the biological response of a group of test organisms to various doses of a toxic agent. They do not necessarily need to be linear and are based on empirical data gathered from experiments on the test organisms. Choices A and C are incorrect as dose-response curves are not typically extrapolated from humans or mathematical models in this context. The statement in option D is incorrect as dose-response curves do not necessarily follow a linear pattern.