(C) Unconventional Dose-Response Curve

Multiple Choice

(c) Unconventional dose-response curve
Use the accompanying figure to answer the following question.
-The flat line at the left in (b) probably represents __________________.

A) no visible effect because the body's physiological processes can cope with low doses of a toxicant
B) that no data were collected for the flatline area
C) competing effects of some other substance whose effect wasn't measured
D) the fact that no toxicant was introduced until the response line begins to rise
E) the fact that there is no physiological effect of the toxicant at low doses