Simpson's Paradox Occurs When

Simpson's Paradox occurs when

A) no baseline risk is given, so it is not know whether or not a high relative risk has practical importance.
B) a confounding variable rather than the explanatory variable is responsible for a change in the response variable.
C) the direction of the relationship between two variables changes when the categories of a confounding variable are taken into account.
D) the results of a test are statistically significant but are really due to chance.